Please wait, CIS 185 will begin shortly… (5:30pm)                                        1
CIS 185 Advanced Routing Protocols          EIGRP Part 2              Rick Graziani              Cabrillo College         ...
EIGRP Part 1   Review                  Frame Relay Bandwidth   Wildcard masks          Distribute Lists   Authenticat...
Thanks Wendell Odom! Much of the information used in this chapter is from the new Cisco  Press BSCI Exam Certification Gu...
Point-to-Pointinterface Serial 0   encapsulation frame-relayinterface Serial 0.1 point-to-point   bandwidth 25   ip bandwi...
Multipointinterface Serial 0   encapsulation frame-relayinterface Serial 0.1 multipoint   bandwidth 224           Lowest s...
Our Topology               Print this out                                7
EIGRP Route Filtering    10.17.32.0/23    10.17.34.0/24    10.17.35.0/25    10.17.32.128/25    10.17.36.0/26    10.17.36.6...
EIGRP Route Filtering ping 172.16.1.10                                                            No route for            ...
EIGRP Route Filtering                Distribute List    ACL           Prefix-List          Route-Map EIGRP uses a distrib...
Route  Filters -  Inbound Router(config-router)#distribute-list access-list-number in    [interface-name]Inbound interface...
Route Filters OutboundRouter(config-router)#distribute-list access-list-number out   [interface-name | routing-process | a...
Route FiltersRTZ(config)# router      eigrp 1RTZ(config-router)#      distribute-list      1   inRTZ(config-router)#      ...
Route Filters - VerificationRTZ(config)#router eigrp 1RTZ(config-router)#distribute-list   1   inRTZ(config-router)#distri...
Route Filters and Link State RoutingProtocols Routers running link state protocols determine their routes based on  infor...
Distribute Lists and ACLs                Distribute List    ACL           Prefix-List          Route-Map EIGRP uses a dis...
DistributeLists andACLsR3(config)# router eigrp 1R3(config-router)# distribute-list 2 out ser 0/2R3(config)# access-list 2...
ACLRangesR3(config)# router eigrp 1R3(config-router)# distribute-list 2 out ser 0/2R3(config)# access-list 2 deny 10.17.32...
ACLRangesR3(config)# access-list 2 deny 10.17.32.0 0.0.7.255Low end                     10.17.32.0Wildcard mask           ...
ACL                         FilteredRangesR3(config)# router eigrp 1R3(config-router)# distribute-list 2 out ser 0/2R3(con...
access-list 3 deny...?access-list       3   deny   10.17.32.0access-list       4   deny   10.17.32.0 0.0.0.255access-list ...
Verifying - BEFORE Distribute ListR4# show ip route | include 10.     10.0.0.0/8 is variably subnetted, 8 subnets, 4 masks...
Verifying – BEFORE Distribute ListR4# show ip route | include 10.17D     10.17.35.0/25 [90/2684416] via 10.0.0.13, 00:04:1...
Distribute ListR3(config)# router eigrp 1R3(config-router)# distribute-list 2 out ser 0/2R3(config)# access-list 2 deny 10...
Verifying Distribute List - AFTERR4# show ip route      172.16.0.0/24 is subnetted, 2 subnetsC        172.16.1.0 is direct...
Verifying Distribute List - AFTERR4# show ip route | include 10.17R4#R1# show ip route | include 10.17D        10.17.35.0/...
Distribute Lists and Prefix Lists                   Distribute List     ACL              Prefix-List              Route-Ma...
Prefix-list conceptsip prefix-list list-name [seq seq-value] {deny | permit  prefix/prefix-length}[ge ge-value] [le le-val...
Prefix-list Conceptsip prefix-list list-name [seq seq-value] {deny | permit  prefix/prefix-length}[ge ge-value] [le le-val...
Prefix-list conceptsip prefix-list list-name [seq seq-value] {deny | permit  prefix/prefix-length}[ge ge-value] [le le-val...
Prefix-list conceptsip prefix-list list-name [seq seq-value] {deny | permit  prefix/prefix-length}[ge ge-value] [le le-val...
Match the Prefix List with the appropriateroutes                  1.   10.0.0.0/8                  2.   10.128.0.0/9      ...
Match the Prefix List with the appropriateroutes                  1.   10.0.0.0/8                  2.   10.128.0.0/9      ...
Match the Prefix List with the appropriateroutes                  1.   10.0.0.0/8                  2.   10.128.0.0/9      ...
Match the Prefix List with the appropriateroutes                 1.   10.0.0.0/8                 2.   10.128.0.0/9        ...
Match the Prefix List with the appropriateroutes                 1.   10.0.0.0/8                 2.   10.128.0.0/9        ...
Match the Prefix List with the appropriateroutes                 1.   10.0.0.0/8                 2.   10.128.0.0/9        ...
Distribute Lists and Prefix Lists                     Distribute List     ACL                Prefix-List                Ro...
DistributeLists andPrefix ListsR3(config)# no access-list 2 deny 10.17.32.0 0.0.7.255R3(config)# no access-list 2 permit a...
Distribute   Lists and                         Filtered   Prefix ListsBEFORER4# show ip route | include 10.   10.0.0.0/8 i...
Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out ...
Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out ...
Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out ...
Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out ...
Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out ...
Verifying   Distribute                        Filtered   Lists and   Prefix ListsBEFORER4# show ip route | include 10.   1...
Verifying Distribute List with Prefix ListAFTERR4# show ip route      172.16.0.0/24 is subnetted, 2 subnetsC        172.16...
Distribute Lists and Route Maps                   Distribute List     ACL              Prefix-List              Route-Map...
Distribute Lists and Route MapsRTZ(config)# router eigrp 1RTZ(config-router)# distribute-list route-map sample-map outRTZ(...
Distribute Lists and Route MapsRTZ(config)# router eigrp 1RTZ(config-router)# distribute-list route-map sample-map outRTZ(...
RTZ(config)# route-map     sample-map    deny 5RTZ(config-route-map)#     match (1st    set of criteria)RTZ(config)# route...
Distribute   Lists and                         Filtered   Route MapsBEFORER4# show ip route | include 10.   10.0.0.0/8 is ...
router eigrp 1   distribute-list route-map filter-lan-slash30 outroute-map    filter-lan-slash30 deny 8    match    ip add...
Verifying Distribute List with Route MapAFTERR4# show ip route      172.16.0.0/24 is subnetted, 2 subnetsC        172.16.1...
EIGRP Summarization andDefault Routes   A CCNA Review
For the rest of this presentation Using information from  the book:    Routing Protocols      and Concepts    By Rick G...
Summarization Benefits:    Smaller routing tables    Reduces Query scope:       EIGRP Query stops at a router which ha...
EIGRP Summarization – Odds and Ends An EIGRP router can summarize routes.    OSPF: Summarization can only take place on ...
The Null0 Summary RouteR1# show ip route   192.168.10.0/24 is variably subnetted, 3 subnets, 2 masksD     192.168.10.0/24 ...
DisablingAutomaticSummarization                                        172.16.0.0/16R3# show ip route   192.168.10.0/24 is...
DisablingAutomatic                                                        172.16.0.0/16Summarization                      ...
DisablingAutomaticSummarization                                        172.16.0.0/16R3# show ip route<output omitted>D   1...
Disabling Automatic SummarizationR1(config)# router eigrp 1R1(config-router)# no auto-summary%DUAL-5-NBRCHANGE: IP-EIGRP(0...
Disabling Automatic SummarizationR1# show ip route    192.168.10.0/30 is subnetted, 2 subnetsC      192.168.10.4 is direct...
Disabling Automatic SummarizationR2# show ip route    192.168.10.0/30 is subnetted, 2 subnetsD      192.168.10.4 [90/35238...
172.16.0.0/16R3# show ip route                                             172.16.0.0/16    192.168.10.0/30 is subnetted, ...
DisablingAutomatic                                                 172.16.0.0/16Summarization                             ...
Manual Summarization EIGRP can be configured to summarize routes, whether or not  automatic summarization (auto-summary) ...
ManualSummarizationR3(config)# interface loopback 2R3(config-if)# ip address 192.168.2.1 255.255.255.0R3(config-if)# inter...
ManualSummarization                                                       192.168.1.0/24,                                 ...
Determining the Summary EIGRP Route1. Write out the networks that you want to summarize in binary.2. Find the matching bit...
Configure EIGRP  Manual                                                            192.168.0.0/22  Summarization          ...
Verify EIGRPManual                                                                  192.168.0.0/22Summarization           ...
Redistribute  EIGRP Default                       Default Route                                                      defau...
RedistributeEIGRP Default                        Default Route                                                         def...
RedistributeEIGRP Default                             Default Route                                                       ...
EIGRP Default Route                                      Redistribute                Default Route                        ...
CIS 185 Advanced Routing Protocols          EIGRP Part 2              Rick Graziani              Cabrillo College         ...
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  • EIGRP automatically includes a Null0 summary route as a child route whenever both of the following conditions exist: There is at least one subnet that was learned via EIGRP . Automatic summarization is enabled . (By default with EIGRP) R1 will discard any packets that match the parent 172.16.0.0/16 classful network but do not match one of the child routes 172.16.1.0/24, 172.16.2.0/24, or 172.16.3.0/24. For example, a packet to 172.16.4.10 would be discarded . This Null0 summary route is a child route that will match any possible packets of the parent route that do not match another child route. This is regardless of ip classless or no ip classless command. Therefore denying the use of any supernet or default route .
  • Like RIP, EIGRP automatically summarizes at major network boundaries using the default auto-summary command.
  • Both R1 and R2 automatically summarized those subnets to the 172.16.0.0/16 classful boundary when sending EIGRP update packets to R3. The result is that R3 has one route to 172.16.0.0/16 through R1. R1 is the successor because of the difference in bandwidth .
  • You can quickly see that this route is not optimal . R3 will route all packets destined for 172.16.2.0 through R1. Across a very slow link to R2 (64 Kbps). Need R1 and R2 to send individual routes for each of the 172.16.0.0/16 subnets . In other words, R1 and R2 must stop automatically summarizing 172.16.0.0/16.
  • Automatic summarization can be disabled with the no auto-summary . The router configuration command eigrp log-neighborchanges is on by default on some IOS implementations. If on, you will see output similar to that shown for R1.
  • R1 no more Null0 summary routes : D 192.168.10.0/24 is a summary, 00:45:09, Null0 D 172.16.0.0/16 is a summary, 00:46:10, Null0 This mean any packets for their parent networks that do not match a child route, the routing table will check supernet and default routes . Unless no ip classess is used
  • R2 no more Null0 summary routes : D 192.168.10.0/24 is a summary, 00:00:15, Null0 D 172.16.0.0/16 is a summary, 00:00:15, Null0
  • Without automatic summarization, R3’s routing table now includes the three subnets: 172.16.1.0/24, 172.16.2.0/24, and 172.16.3.0/24. Why does R3’s routing table now have two equal-cost paths to 172.16.3.0/24? Shouldn’t the best path only be through R1 with the 1544-Mbps link?
  • The slowest link is the 64-Kbps link that contains the 172.16.3.0/30 network. The 1544-Mbps link and the 1024-Kbps link are irrelevant in the calculation as far as the bandwidth metric is concerned.
  • EIGRP can be configured to summarize routes, whether or not automatic summarization ( auto-summary ) is enabled. Modified topology.
  • Add two more networks to R3 . With the appropriate network commands R3 will propagate these networks to other routers.
  • R1 and R2 routing tables show these additional networks in their routing tables . Instead of sending three separate networks, R3 can summarize the 192.168.1.0/24, 192.168.2.0/24, and 192.168.3.0/24 networks as a single route .
  • 1. Write out the networks that you want to summarize in binary . 2. Find the matching bits . Count the number of leftmost matching bits, which in this example is 22. This number becomes your subnet mask for the summarized route: /22 or 255.255.252.0. 3. To find the network address for summarization, copy the matching 22 bits and add all 0 bits to the end to make 32 bits. The result is the summary network address and mask for 192.168.0.0/22
  • Because R3 has two EIGRP neighbors, the EIGRP manual summarization in configured on both Serial 0/0/0 and Serial 0/0/1 .
  • Summary routes lessen the number of total routes in routing tables, which makes the routing table lookup process more efficient. Summary routes also require less bandwidth utilization for the routing updates because a single route can be sent rather than multiple individual routes.
  • Using a static route to 0.0.0.0/0 as a default route is not routing protocol dependent. The “quad zero” static default route can be used with any currently supported routing protocols. EIGRP requires the use of the redistribute static command to include this static default route with its EIGRP routing updates.
  • In the routing tables for R1 and R3, notice the routing source and AD for the new static default route. D : This static route was learned from an EIGRP routing update . * : The route is a candidate for a default route. EX: The route is an external EIGRP route , in this case a static route outside of the EIGRP routing domain. 170: This is the AD of an external EIGRP route.
  • There is another method to propagate a default route in EIGRP, using the ip default-network command. More information on this command can be found at this site: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml.
  • Cis185 bsci-lecture3-eigrp-part2

    1. 1. Please wait, CIS 185 will begin shortly… (5:30pm) 1
    2. 2. CIS 185 Advanced Routing Protocols EIGRP Part 2 Rick Graziani Cabrillo College graziani@cabrillo.edu Last Updated: Fall 2009
    3. 3. EIGRP Part 1 Review  Frame Relay Bandwidth Wildcard masks  Distribute Lists Authentication  With ACLs Passive Interfaces  With Prefix-Lists Stuck-in-active  With Route Maps Stub Routers  Summarization Offsets  Default Route Variance Ip-bandwidth percent 3
    4. 4. Thanks Wendell Odom! Much of the information used in this chapter is from the new Cisco Press BSCI Exam Certification Guide by Wendell Odom. (Not yet released at the time of this writing.) I highly recommend this book! 4
    5. 5. Point-to-Pointinterface Serial 0 encapsulation frame-relayinterface Serial 0.1 point-to-point bandwidth 25 ip bandwidth-percent eigrp 123 90 256 / 10 = 25…interface Serial 0.10 point-to-point bandwidth 25 ip bandwidth-percent eigrp 123 90  Because there is a maximum of 256Kbps available on the access circuit, we cannot allow any individual PVC to handle more than 25Kbps (256/10).  Since this data rate is fairly low, and we dont expect very much user data traffic, we can allow EIGRP to use up to 90% of the bandwidth. 5
    6. 6. Multipointinterface Serial 0 encapsulation frame-relayinterface Serial 0.1 multipoint bandwidth 224 Lowest speed connection = 56 Kbps 4 * 56 = 224If the virtual circuits are of different capacities, The bandwidth must be set to take into account the lowest capacity virtual circuit. Example, if a T1 access line has three 256Kbps VCs and one 56Kbps VC, the bandwidth should be set to 224Kbps (4 * 56Kbps). Bandwidth equals the CIR rate of the lowest speed connection multiplied by the number of circuits. 6
    7. 7. Our Topology Print this out 7
    8. 8. EIGRP Route Filtering 10.17.32.0/23 10.17.34.0/24 10.17.35.0/25 10.17.32.128/25 10.17.36.0/26 10.17.36.64/26 10.17.32.0/23 10.17.34.0/24 Route Filtering  Allows an engineer to filter which routes are advertised in an EIGRP update. Reasons  Branch Offices only need to communicate with Headquarters, not with each other.  Smaller Routing Tables  Security 8
    9. 9. EIGRP Route Filtering ping 172.16.1.10 No route for 10.17.35.0/25 DROP REPLY Drawback  Network engineers have the additional troubleshooting challenge deciding whether it was due to a failure in the network or because of their design decision. 9
    10. 10. EIGRP Route Filtering Distribute List ACL Prefix-List Route-Map EIGRP uses a distribute-list router subcommand. Distribute List refers to:  ACL  Prefix List  Route Map  Uses an ACL or Prefix List 10
    11. 11. Route Filters - Inbound Router(config-router)#distribute-list access-list-number in [interface-name]Inbound interfaces: Affects only the routing updates inbound on that interface. Same update may come from another interface from the same (LAN) or different (serial) router. Note: This does not permit/deny other packets from entering the routers, only which updates a router will send or receive. 11
    12. 12. Route Filters OutboundRouter(config-router)#distribute-list access-list-number out [interface-name | routing-process | as-number]Outbound interfaces: Affects only the routing updates outbound on that interface. 12
    13. 13. Route FiltersRTZ(config)# router eigrp 1RTZ(config-router)# distribute-list 1 inRTZ(config-router)# distribute-list 2 outRTZ(config-router)# distribute-list 3 in serial 0/0RTZ(config-router)# distribute-list 4 out serial 0/0 For each interface and routing process, Cisco IOS permits: • One incoming global distribute-list • One outgoing global distribute-list • One incoming distribute-list per interface • One outgoing distribute-list per interface 13
    14. 14. Route Filters - VerificationRTZ(config)#router eigrp 1RTZ(config-router)#distribute-list 1 inRTZ(config-router)#distribute-list 2 outRTZ(config-router)#distribute-list 3 in e0RTZ(config-router)#distribute-list 4 out e0RTZ#show ip protocolsRouting Protocol is "rip" Sending updates every 30 seconds, next due in 25 seconds Invalid after 180 seconds, hold down 180, flushed after 240 Outgoing update filter list for all interfaces is 2 Ethernet0 filtered by 4 Incoming update filter list for all interfaces is 1 Ethernet0 filtered by 3 14
    15. 15. Route Filters and Link State RoutingProtocols Routers running link state protocols determine their routes based on information in their link state database, rather than the advertised route entries of its neighbors. Route filters have a different effect on link state advertisements or the link state database.  Remember, a basic requirement of link state routing protocols is that routers in an area must have identical link state databases. We will examine route filters and link state routing protocols later with OSPF. 15
    16. 16. Distribute Lists and ACLs Distribute List ACL Prefix-List Route-Map EIGRP uses a distribute-list router subcommand. Distribute List refers to:  ACL  Prefix List  Route Map  Uses an ACL or Prefix List 16
    17. 17. DistributeLists andACLsR3(config)# router eigrp 1R3(config-router)# distribute-list 2 out ser 0/2R3(config)# access-list 2 deny 10.17.35.0 0.0.0.127R3(config)# access-list 2 permit any Objective: Deny R4 from learning about the 10.17.35.0/25 network. Create a distribute-list outbound serial 0/2  Refer to access-list 2 To filter EIGRP routes using an ACL:  ACL deny – filters the route  ACL permit - allows route to be advertised 17
    18. 18. ACLRangesR3(config)# router eigrp 1R3(config-router)# distribute-list 2 out ser 0/2R3(config)# access-list 2 deny 10.17.32.0 0.0.7.255R3(config)# access-list 2 permit any What if we needed to filter a range of networks? We could use several ACL statements or use the wildcard mask to specify a range. What range of networks does this network/wildcard mask summarize? 18
    19. 19. ACLRangesR3(config)# access-list 2 deny 10.17.32.0 0.0.7.255Low end 10.17.32.0Wildcard mask + 0. 0. 7.255 --------------High end 10.17.39.255 It’s easy! Start with the addresses in ACL which is the low end: 10.17.32.0 Add the wildcard mask: 0.0.7.255 The result is the high end of the range! ACL range: 10.17.32.0 through 10.17.39.255 19
    20. 20. ACL FilteredRangesR3(config)# router eigrp 1R3(config-router)# distribute-list 2 out ser 0/2R3(config)# access-list 2 deny 10.17.32.0 0.0.7.255R3(config)# access-list 2 permit any This distribute list filters all EIGRP updates for the LANs, 10.17.32.0 through 10.17.36.64, going to R4  ACL range: 10.17.32.0 through 10.17.39.255 20
    21. 21. access-list 3 deny...?access-list 3 deny 10.17.32.0access-list 4 deny 10.17.32.0 0.0.0.255access-list 5 deny 10.17.32.0 0.0.3.255access-list 6 deny 10.16.0.0 0.1.255.255 What address or range of addresses do these ACLs deny?  Exactly the prefix 10.17.32.0, (does not match any other routes)  All prefixes that begin "10.17.32“, 10.17.32.0 – 10.17.32.255.  All prefixes in the range 10.17.32.0 – 10.17.35.255.  All prefixes in the range 10.16.0.0 – 10.17.255.255 ACL range: 10.17.32.0 through 10.17.39.255 21
    22. 22. Verifying - BEFORE Distribute ListR4# show ip route | include 10. 10.0.0.0/8 is variably subnetted, 8 subnets, 4 masksD 10.0.0.8/30 [90/2681856] via 10.0.0.13, 00:06:28, Ser0/0C 10.0.0.12/30 is directly connected, Serial0/0D 10.0.0.0/30 [90/3193856] via 10.0.0.13, 00:06:28, Ser0/0D 10.0.0.4/30 [90/2681856] via 10.0.0.13, 00:06:28, Ser0/0D 10.17.35.0/25 [90/2684416] via 10.0.0.13, 00:06:15, Ser0/0D 10.17.34.0/24 [90/2684416] via 10.0.0.13, 00:03:04, Ser0/0D 10.17.32.0/23 [90/2684416] via 10.0.0.13, 00:05:58, Ser0/0D 10.17.36.0/26 [90/2172416] via 10.0.0.13, 00:06:28, Ser0/0D 10.17.36.64/26 [90/2172416] via 10.0.0.13, 00:06:28,Ser0/0  Notice the option with the pipe! 22
    23. 23. Verifying – BEFORE Distribute ListR4# show ip route | include 10.17D 10.17.35.0/25 [90/2684416] via 10.0.0.13, 00:04:16, Ser0/0D 10.17.34.0/24 [90/2684416] via 10.0.0.13, 00:03:04, Ser0/0D 10.17.32.0/23 [90/2684416] via 10.0.0.13, 00:03:59, Ser0/0D 10.17.36.0/26 [90/2172416] via 10.0.0.13, 00:04:29, Ser0/0D 10.17.36.64/26 [90/2172416] via 10.0.0.13, 00:04:29,Ser0/0 23
    24. 24. Distribute ListR3(config)# router eigrp 1R3(config-router)# distribute-list 2 out ser 0/2R3(config)# access-list 2 deny 10.17.32.0 0.0.7.255R3(config)# access-list 2 permit any01:31:34: %DUAL-5-NBRCHANGE: IP-EIGRP 1: Neighbor 10.0.0.14 (Serial0/2) is down: route configuration changed01:31:38: %DUAL-5-NBRCHANGE: IP-EIGRP 1: Neighbor 10.0.0.14 (Serial0/2) is up: new adjacency This distribute list filters all EIGRP updates for the LANs, 10.17.32.0 through 10.17.36.64, going to R4.  ACL range: 10.17.32.0 through 10.17.39.255 24
    25. 25. Verifying Distribute List - AFTERR4# show ip route 172.16.0.0/24 is subnetted, 2 subnetsC 172.16.1.0 is directly connected, FastEthernet0/0C 172.16.2.0 is directly connected, FastEthernet0/1 10.0.0.0/30 is subnetted, 4 subnetsD 10.0.0.8 [90/2681856] via 10.0.0.13, 00:01:26, Serial0/0C 10.0.0.12 is directly connected, Serial0/0D 10.0.0.0 [90/3193856] via 10.0.0.13, 00:01:26, Serial0/0D 10.0.0.4 [90/2681856] via 10.0.0.13, 00:01:26, Serial0/0  Only has serial “10” networks which were not in the range ACL range: 10.17.32.0 through 10.17.36.64  ACL range: 10.17.32.0 through 10.17.39.255 25
    26. 26. Verifying Distribute List - AFTERR4# show ip route | include 10.17R4#R1# show ip route | include 10.17D 10.17.35.0/25 [90/2172416] via 10.0.0.2, 00:25:50, Ser0/0C 10.17.34.0/24 is directly connected, FastEthernet0/1C 10.17.32.0/23 is directly connected, FastEthernet0/0D 10.17.36.0/26 [90/2172416] via 10.0.0.6, 00:25:50, Ser0/1D 10.17.36.64/26 [90/2172416] via 10.0.0.6, 00:25:50,Ser0/1R1#  R4 does not have any of the “10.17” routes.  R1 still has all the routes, including the “10.17” routes. 26
    27. 27. Distribute Lists and Prefix Lists Distribute List ACL Prefix-List Route-Map Prefix-list uses a distribute-list router subcommand. Another tool for matching routes. Can examine both the prefix (network address) and the prefix length (subnet mask).  Or a range of ether ACLs matched only the prefix of the route (subnet number), IP prefix lists always examine both the prefix and prefix length. 27
    28. 28. Prefix-list conceptsip prefix-list list-name [seq seq-value] {deny | permit prefix/prefix-length}[ge ge-value] [le le-value]  The route prefix (the subnet number)  The prefix length (the subnet mask)  Each command has a permit or deny action  Only used for matching routes.  Not used for packet filtering.  Just implies whether a route is matched (permit) or not (deny).  Sequence numbers are used for the insertion and deletion of individual commands. 28
    29. 29. Prefix-list Conceptsip prefix-list list-name [seq seq-value] {deny | permit prefix/prefix-length}[ge ge-value] [le le-value]  Prefix-list Logic: 1. The route’s prefix must be within the range of addresses implied by the prefix-list command’s prefix/prefix-length parameters. 2. The route’s prefix length must match the range of prefixes implied by the prefix-list commands prefix-length, ge, and le parameters.  What??? 29
    30. 30. Prefix-list conceptsip prefix-list list-name [seq seq-value] {deny | permit prefix/prefix-length}[ge ge-value] [le le-value] Examining the Prefix  prefix/prefix-length –  Prefix: Address to be used for matching.  Prefix length: How much of the address must match.  10.0.0.0/8  Any number (address) whose first 8 bits (/8) match 10.0.0.0.  Examples coming soon! 30
    31. 31. Prefix-list conceptsip prefix-list list-name [seq seq-value] {deny | permit prefix/prefix-length}[ge ge-value] [le le-value] Examining the Prefix Length  Blank: Exact match.  ge ge-value: Subnet mask must be at least this length up to /32.  le le-value: Subnet mask must be this length or less, but at least the length of the prefix-length.  ge ge-value le le-value: Subnet mask must fall within this range  The ge value must be larger than the configured prefix length in the base part of the command.  ip prefix-list list1 permit 1.0.0.0/8 ge 7 would be rejected  The ge value (7) is less than the configured prefix-length (/8).  Examples coming next! 31
    32. 32. Match the Prefix List with the appropriateroutes 1. 10.0.0.0/8 2. 10.128.0.0/9 3. 10.1.1.0/24 4. 10.1.2.0/24 5. 10.128.10.4/30 6. 10.128.10.8/3010.0.0.0/8 Routes matched: 1 Reason: Without ge or le configured, both the prefix (10.0.0.0) and length (8) must be an exact match. 32
    33. 33. Match the Prefix List with the appropriateroutes 1. 10.0.0.0/8 2. 10.128.0.0/9 3. 10.1.1.0/24 4. 10.1.2.0/24 5. 10.128.10.4/30 6. 10.128.10.8/3010.0.0.0/8 ge 9 Routes matched: 2 - 6 Reason: The 10.0.0.0/8 means “all routes whose first octet is 10”. The prefix length must be between 9 and 32, inclusive. 33
    34. 34. Match the Prefix List with the appropriateroutes 1. 10.0.0.0/8 2. 10.128.0.0/9 3. 10.1.1.0/24 4. 10.1.2.0/24 5. 10.128.10.4/30 6. 10.128.10.8/3010.0.0.0/8 ge 24 le 24 Routes matched: 3, 4 Reason: The 10.0.0.0/8 means “all routes whose first octet is 10,” and the prefix range is 24 to 24 — meaning only routes with prefix length 24. 34
    35. 35. Match the Prefix List with the appropriateroutes 1. 10.0.0.0/8 2. 10.128.0.0/9 3. 10.1.1.0/24 4. 10.1.2.0/24 5. 10.128.10.4/30 6. 10.128.10.8/3010.0.0.0/8 le 28 Routes matched: 1 - 4 Reason: The prefix length needs to be between 8 and 28, inclusive. 35
    36. 36. Match the Prefix List with the appropriateroutes 1. 10.0.0.0/8 2. 10.128.0.0/9 3. 10.1.1.0/24 4. 10.1.2.0/24 5. 10.128.10.4/30 6. 10.128.10.8/300.0.0.0/0 Routes matched: none Reason:  0.0.0.0/0 means “match all prefixes”.  Because no le nor ge parameter is configured, the /0 also means that the prefix length must be exactly 0.  Only a default route would match this prefix list. 36
    37. 37. Match the Prefix List with the appropriateroutes 1. 10.0.0.0/8 2. 10.128.0.0/9 3. 10.1.1.0/24 4. 10.1.2.0/24 5. 10.128.10.4/30 6. 10.128.10.8/300.0.0.0/0 le 32 Routes matched: All Reason:  The range implied by 0.0.0.0/0 is all IPv4 addresses.  The le 32 then implies any prefix length between 0 and 32, inclusive.  This is the syntax for “match all” prefix list logic. 37
    38. 38. Distribute Lists and Prefix Lists Distribute List ACL Prefix-List Route-Map Using the prefix-list with the distribute list is easy now! 38
    39. 39. DistributeLists andPrefix ListsR3(config)# no access-list 2 deny 10.17.32.0 0.0.7.255R3(config)# no access-list 2 permit anyR3(config)# router eigrp 1R3(config-router)# no distribute-list 2 out ser 0/2 Remove the previous distribute list and ACLs if appropriate. 39
    40. 40. Distribute Lists and Filtered Prefix ListsBEFORER4# show ip route | include 10. 10.0.0.0/8 is variably subnetted, 8 subnets, 4 masksD 10.0.0.8/30 [90/2681856] via 10.0.0.13, 00:02:34, Serial0/0C 10.0.0.12/30 is directly connected, Serial0/0 Not FilteredD 10.0.0.0/30 [90/3193856] via 10.0.0.13, 00:02:30, Serial0/0D 10.0.0.4/30 [90/2681856] via 10.0.0.13, 00:02:34, Serial0/0D 10.17.35.0/25 [90/2684416] via 10.0.0.13, 00:02:31, Serial0/0D 10.17.34.0/24 [90/2684416] via 10.0.0.13, 00:03:04, Serial0/0D 10.17.32.0/23 [90/2684416] via 10.0.0.13, 00:02:31, Serial0/0D 10.17.36.0/26 [90/2172416] via 10.0.0.13, 00:02:36, Serial0/0D 10.17.36.64/26 [90/2172416] via 10.0.0.13, 00:02:36, Serial0/0 Objectives - Routes going to R4:  Filter only those routes which begin with 10.17.35 with a /25 mask and 10.17.36 with a /26 mask.  Filter /30 routes 40
    41. 41. Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out Serial0/2R3(config)# ip prefix-list no-r1-r2-slash30 seq 5 deny 10.17.35.0/24 ge 25 le 25R3(config)# ip prefix-list no-r1-r2-slash30 seq 10 deny 10.17.36.0/24 ge 26 le 26R3(config)# ip prefix-list no-r1-r2-slash30 seq 15 deny 0.0.0.0/0 ge 30 le 30R3(config)# ip prefix-list no-r1-r2-slash30 seq 20 permit 0.0.0.0/0 le 32 Objectives - Routes going to R4:  Filter only those routes which begin with 10.17.35 with a /25 mask and 10.17.36 with a /26 mask.  Filter /30 routes 41
    42. 42. Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out Serial0/2R3(config)# ip prefix-list no-r1-r2-slash30 seq 5 deny 10.17.35.0/24 ge 25 le 25 Sequence number 5 - Matches 10.17.35.0/25 and 10.17.35.128/25 • Matches prefix: 24 bits of 10.17.35 routes. • Matches prefix-lists: exactly /25. 42
    43. 43. Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out Serial0/2R3(config)# ip prefix-list no-r1-r2-slash30 seq 5 deny 10.17.35.0/24 ge 25 le 25R3(config)# ip prefix-list no-r1-r2-slash30 seq 10 deny 10.17.36.0/24 ge 26 le 26 Sequence number 10 - Matches routes 10.17.36.0/26 and 10.17.36.64/26. • Matches prefix: 24 bits of 10.17.36 routes. • Matches prefix-lists: exactly /26. 43
    44. 44. Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out Serial0/2R3(config)# ip prefix-list no-r1-r2-slash30 seq 5 deny 10.17.35.0/24 ge 25 le 25R3(config)# ip prefix-list no-r1-r2-slash30 seq 10 deny 10.17.36.0/24 ge 26 le 26R3(config)# ip prefix-list no-r1-r2-slash30 seq 15 deny 0.0.0.0/0 ge 30 le 30 Sequence number 15 - uses wildcard logic (0.0.0.0/0) to match all. • Matches prefix: Match all (0.0.0.0/0). • Matches prefix-lists: exactly /30. 44
    45. 45. Distribute Lists and Prefix ListsR3(config)# router eigrp 1R3(config-router)# distribute-list prefix no-r1-r2-slash30 out Serial0/2R3(config)# ip prefix-list no-r1-r2-slash30 seq 5 deny 10.17.35.0/24 ge 25 le 25R3(config)# ip prefix-list no-r1-r2-slash30 seq 10 deny 10.17.36.0/24 ge 26 le 26R3(config)# ip prefix-list no-r1-r2-slash30 seq 15 deny 0.0.0.0/0 ge 30 le 30R3(config)# ip prefix-list no-r1-r2-slash30 seq 20 permit 0.0.0.0/0 le 32 Sequence number 20 - uses wildcard logic (0.0.0.0/0) to match all. • Matches prefix: Match all (0.0.0.0/0). • Matches prefix-lists: All prefixes (le 32). 45
    46. 46. Verifying Distribute Filtered Lists and Prefix ListsBEFORER4# show ip route | include 10. 10.0.0.0/8 is variably subnetted, 8 subnets, 4 masksD 10.0.0.8/30 [90/2681856] via 10.0.0.13, 00:02:34, Serial0/0C 10.0.0.12/30 is directly connected, Serial0/0 Not FilteredD 10.0.0.0/30 [90/3193856] via 10.0.0.13, 00:02:30, Serial0/0D 10.0.0.4/30 [90/2681856] via 10.0.0.13, 00:02:34, Serial0/0D 10.17.35.0/25 [90/2684416] via 10.0.0.13, 00:02:31, Serial0/0D 10.17.34.0/24 [90/2684416] via 10.0.0.13, 00:03:04, Serial0/0D 10.17.32.0/23 [90/2684416] via 10.0.0.13, 00:02:31, Serial0/0D 10.17.36.0/26 [90/2172416] via 10.0.0.13, 00:02:36, Serial0/0D 10.17.36.64/26 [90/2172416] via 10.0.0.13, 00:02:36, Serial0/0 Objectives - Routes going to R4:  Filter only those routes which begin with 10.17.35 with a /25 mask and 10.17.36 with a /26 mask.  Filter /30 routes 46
    47. 47. Verifying Distribute List with Prefix ListAFTERR4# show ip route 172.16.0.0/24 is subnetted, 2 subnetsC 172.16.1.0 is directly connected, FastEthernet0/0C 172.16.2.0 is directly connected, FastEthernet0/1 10.0.0.0/8 is variably subnetted, 3 subnets, 3 masksC 10.0.0.12/30 is directly connected, Serial0/0D 10.17.34.0/24 [90/2684416] via 10.0.0.13, 00:03:04, Serial0/0D 10.17.32.0/23 [90/2684416] via 10.0.0.13, 00:08:59, Serial0/0Objectives - Routes going to R4: Filter only those routes which begin with 10.17.35 with a /25 mask and 10.17.36 with a /26 mask. Filter /30 routes 47
    48. 48. Distribute Lists and Route Maps Distribute List ACL Prefix-List Route-Map Route maps are used for various things including:  Policy Routing – Sophisticated static routes  Route Filtering during redistribution  Setting BGP attributes  Route Filtering with distribute lists Similar logic to the If/Then/Else logic seen in programming languages. Additional features but can be tricky to configure. 48
    49. 49. Distribute Lists and Route MapsRTZ(config)# router eigrp 1RTZ(config-router)# distribute-list route-map sample-map outRTZ(config)# route-map sample-map deny 5RTZ(config-route-map)# match (1st set of criteria)RTZ(config)# route-map sample-map permit 10RTZ(config-route-map)# match (2nd set of criteria)RTZ(config)# route-map sample-map deny 30RTZ(config-route-map)# match (3rd set of criteria)RTZ(config)# route-map sample-map permit 35 Seq #5: deny, discard or filter all routes matched by the match command (1st set of criteria) Seq #10: permit, allow through all routes matched by the match command (2nd set of criteria) Seq #30: deny, discard or filter all routes matched by the match command (3rd set of criteria) Seq #35: permit. The absence of a match command means "match all", so allow through all remaining routes 49
    50. 50. Distribute Lists and Route MapsRTZ(config)# router eigrp 1RTZ(config-router)# distribute-list route-map sample-map outRTZ(config)# route-map sample-map deny 5RTZ(config-route-map)# match (1st set of criteria)RTZ(config)# route-map sample-map permit 10RTZ(config-route-map)# match (2nd set of criteria)RTZ(config)# route-map sample-map deny 30RTZ(config-route-map)# match (3rd set of criteria)RTZ(config)# route-map sample-map permit 35 Match command references:  ACL  Prefix List IMPORTANT: The decision to filter a route or allow the route through is based on the deny or permit in the route-map command, and not the deny or permit in the ACL or prefix list. 50
    51. 51. RTZ(config)# route-map sample-map deny 5RTZ(config-route-map)# match (1st set of criteria)RTZ(config)# route-map sample-map permit 10RTZ(config-route-map)# match (2nd set of criteria)RTZ(config)# route-map sample-map deny 30RTZ(config-route-map)# match (3rd set of criteria)RTZ(config)# route-map sample-map permit 35  Route-map with permit  Match: Allow route to go through  No match: Remain in the list and go to next route-map command  Route-map with deny  Match: Filter the route  No match: Remain in the list and go to next route-map command  If match command refers to ACL or Prefix List with a:  Permit: If there is a match proceed with permit/deny in route-map.  Deny: Not necessarily filtered, just doesn’t match and proceed to next match command. (Less common) 51
    52. 52. Distribute Lists and Filtered Route MapsBEFORER4# show ip route | include 10. 10.0.0.0/8 is variably subnetted, 8 subnets, 4 masksD 10.0.0.8/30 [90/2681856] via 10.0.0.13, 00:02:34, Serial0/0C 10.0.0.12/30 is directly connected, Serial0/0 Not FilteredD 10.0.0.0/30 [90/3193856] via 10.0.0.13, 00:02:30, Serial0/0D 10.0.0.4/30 [90/2681856] via 10.0.0.13, 00:02:34, Serial0/0D 10.17.35.0/25 [90/2684416] via 10.0.0.13, 00:02:31, Serial0/0D 10.17.34.0/24 [90/2684416] via 10.0.0.13, 00:03:04, Serial0/0D 10.17.32.0/23 [90/2684416] via 10.0.0.13, 00:02:31, Serial0/0D 10.17.36.0/26 [90/2172416] via 10.0.0.13, 00:02:36, Serial0/0D 10.17.36.64/26 [90/2172416] via 10.0.0.13, 00:02:36, Serial0/0 Objectives - Routes going to R4: (Same as before)  Filter only those routes which begin with 10.17.35 with a /25 mask and 10.17.36 with a /26 mask.  Filter /30 routes 52
    53. 53. router eigrp 1 distribute-list route-map filter-lan-slash30 outroute-map filter-lan-slash30 deny 8 match ip address prefix-list lansroute-map filter-lan-slash30 deny 15 match ip address prefix-list slash30route-map filter-lan-slash30 permit 23ip prefix-list lans seq 5 permit 10.17.35.0/24 ge 25 le 25ip prefix-list lans seq 10 permit 10.17.36.0/24 ge 26 le 26ip prefix-list slash30 seq 5 permit 0.0.0.0/0 ge 30 le 30  Filter (deny) routes that match the prefix-list:  10.17.35.0/25  10.17.36.0/26  Filter (deny) routes that match the prefix-list: All /30 routes.  route-map with a permit action and no match command:  Default action is to allow the route to be advertised. 53
    54. 54. Verifying Distribute List with Route MapAFTERR4# show ip route 172.16.0.0/24 is subnetted, 2 subnetsC 172.16.1.0 is directly connected, FastEthernet0/0C 172.16.2.0 is directly connected, FastEthernet0/1 10.0.0.0/8 is variably subnetted, 3 subnets, 3 masksC 10.0.0.12/30 is directly connected, Serial0/0D 10.17.34.0/24 [90/2684416] via 10.0.0.13, 00:03:04, Serial0/0D 10.17.32.0/23 [90/2684416] via 10.0.0.13, 00:08:59, Serial0/0Objectives - Routes going to R4: Filter only those routes which begin with 10.17.35 with a /25 mask and 10.17.36 with a /26 mask. Filter /30 routes 54
    55. 55. EIGRP Summarization andDefault Routes A CCNA Review
    56. 56. For the rest of this presentation Using information from the book:  Routing Protocols and Concepts  By Rick Graziani and Allan Johnson  ISBN: 1-58713- 206-0  ISBN-13: 978- 58713-206-3 A great gift for a loved one!  56
    57. 57. Summarization Benefits:  Smaller routing tables  Reduces Query scope:  EIGRP Query stops at a router which has a summary route that includes the subnet listed in the Query, but not the specific route listed in the Query  EIGRP supports summarization on any router in the network Trade-offs:  Can cause suboptimal routing  Packets destined for inaccessible destinations will flow to the summarizing router before being discarded Note: If a packet matches two routes in the routing table, the best match will be the route with the longest-bit-match, the route with the longer prefix-length (subnet mask). 57
    58. 58. EIGRP Summarization – Odds and Ends An EIGRP router can summarize routes.  OSPF: Summarization can only take place on the ABRs and ASBRs. The summary routes metric is based on the lowest metric route upon which the summary route is based.  The summary route will us a metric equal to the metric of the lowest metric subordinate route. Manual summarization creates a Null0 summary on the router doing the summarization.R3(config)# interface serial 0/0/1R3(config-if)# ip summary-address eigrp 1 192.168.0.0 255.255.252.0R3# show ip route Creates a Null0 summary route<output omitted>D 192.168.0.0/22 is a summary, 00:00:06, Null0 58
    59. 59. The Null0 Summary RouteR1# show ip route 192.168.10.0/24 is variably subnetted, 3 subnets, 2 masksD 192.168.10.0/24 is a summary, 00:45:09, Null0C 192.168.10.4/30 is directly connected, Serial0/0/1D 192.168.10.8/30 [90/3523840] via 192.168.10.6, 00:44:56, S0/0/1 172.16.0.0/16 is variably subnetted, 4 subnets, 3 masksD 172.16.0.0/16 is a summary, 00:46:10, Null0C 172.16.1.0/24 is directly connected, FastEthernet0/0D 172.16.2.0/24 [90/40514560] via 172.16.3.2, 00:45:09, S0/0/0C 172.16.3.0/30 is directly connected, Serial0/0/0D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 00:44:55, Serial0/0/1 EIGRP automatically includes a Null0 summary route as a child route whenever both of the following conditions exist:  There is at least one subnet that was learned via EIGRP.  Automatic summarization is enabled. (By default with EIGRP) What if R1 received a packet: 172.16.4.10  It would be discarded – never looking for a supernet or default route  Regardless of ip classless or no ip classless command59
    60. 60. DisablingAutomaticSummarization 172.16.0.0/16R3# show ip route 192.168.10.0/24 is variably subnetted, 3 subnets, 2 masksD 192.168.10.0/24 is a summary, 01:08:35, Null0C 192.168.10.4/30 is directly connected, Serial0/0/0C 192.168.10.8/30 is directly connected, Serial0/0/1D 172.16.0.0/16 [90/2172416] via 192.168.10.5, 01:08:30, Serial0/0/0C 192.168.1.0/24 is directly connected, FastEthernet0/0 Like RIP, EIGRP automatically summarizes at major network boundaries using the default auto-summary command. 60
    61. 61. DisablingAutomatic 172.16.0.0/16Summarization 172.16.0.0/16R3# show ip route 192.168.10.0/24 is variably subnetted, 3 subnets, 2 masksD 192.168.10.0/24 is a summary, 01:08:35, Null0C 192.168.10.4/30 is directly connected, Serial0/0/0C 192.168.10.8/30 is directly connected, Serial0/0/1D 172.16.0.0/16 [90/2172416] via 192.168.10.5, 01:08:30, Serial0/0/0C 192.168.1.0/24 is directly connected, FastEthernet0/0 Both R1 and R2 automatically summarizing. R1 is the successor because of the difference in bandwidth. 61
    62. 62. DisablingAutomaticSummarization 172.16.0.0/16R3# show ip route<output omitted>D 172.16.0.0/16 [90/2172416] via 192.168.10.5, 01:08:30, Serial0/0/0 Is this the best route for all 172.16.0.0 subnets?  No, suboptimal routing may occur.  R3 will route all packets destined for 172.16.2.0 through R1. Solution?  Need R1 and R2 to send individual subnets.  R1 and R2 must stop automatically summarizing 172.16.0.0/16. 62
    63. 63. Disabling Automatic SummarizationR1(config)# router eigrp 1R1(config-router)# no auto-summary%DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.3.2 (Serial0/0/0) is resync: summary configured%DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.3.2 (Serial0/0/0) is down: peer restarted%DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.3.2 (Serial0/0/0) is up: new adjacency<output omitted>R2(config)# router eigrp 1R2(config-router)# no auto-summaryR3(config)# router eigrp 1R3(config-router)# no auto-summary Automatic summarization can be disabled with the no auto-summary. The router configuration command eigrp log-neighborchanges is on by default on some IOS implementations. . 63
    64. 64. Disabling Automatic SummarizationR1# show ip route 192.168.10.0/30 is subnetted, 2 subnetsC 192.168.10.4 is directly connected, Serial0/0/1D 192.168.10.8 [90/3523840] via 192.168.10.6, 00:16:55, S0/0/1 172.16.0.0/16 is variably subnetted, 3 subnets, 2 masksC 172.16.1.0/24 is directly connected, FastEthernet0/0D 172.16.2.0/24 [90/3526400] via 192.168.10.6, 00:16:53, S0/0/1C 172.16.3.0/30 is directly connected, Serial0/0/0D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 00:16:52, Serial0/0/1 R1 no more Null0 summary routes:D 192.168.10.0/24 is a summary, 00:45:09, Null0D 172.16.0.0/16 is a summary, 00:46:10, Null0 What does this mean?  This mean any packets for their parent networks that do not match a child route, the routing table will check supernet and default routes.  Unless no ip classess is used 64
    65. 65. Disabling Automatic SummarizationR2# show ip route 192.168.10.0/30 is subnetted, 2 subnetsD 192.168.10.4 [90/3523840] via 192.168.10.10, 00:15:44, S0/0/1C 192.168.10.8 is directly connected, Serial0/0/1 172.16.0.0/16 is variably subnetted, 3 subnets, 2 masksD 172.16.1.0/24 [90/3526400] via 192.168.10.10, 00:15:44, S0/0/1C 172.16.2.0/24 is directly connected, FastEthernet0/0C 172.16.3.0/30 is directly connected, Serial0/0/0 10.0.0.0/30 is subnetted, 1 subnetsC 10.1.1.0 is directly connected, Loopback1D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 00:15:44, S0/0/1 R2 no more Null0 summary routes :D 192.168.10.0/24 is a summary, 00:00:15, Null0D 172.16.0.0/16 is a summary, 00:00:15, Null0 65
    66. 66. 172.16.0.0/16R3# show ip route 172.16.0.0/16 192.168.10.0/30 is subnetted, 2 subnetsC 192.168.10.4 is directly connected, Serial0/0/0C 192.168.10.8 is directly connected, Serial0/0/1 172.16.0.0/16 is variably subnetted, 3 subnets, 2 masksD 172.16.1.0/24 [90/2172416] via 192.168.10.5, 00:00:11, S0/0/0D 172.16.2.0/24 [90/3014400] via 192.168.10.9, 00:00:12, S0/0/1D 172.16.3.0/30 [90/41024000] via 192.168.10.5, 00:00:12, S0/0/0 [90/41024000] via 192.168.10.9, 00:00:12, S0/0/1C 192.168.1.0/24 is directly connected, FastEthernet0/0 Why does R3’s routing table now have two equal-cost paths to 172.16.3.0/24? 66  Shouldn’t the best path only be through R1 with the 1544-Mbps link?
    67. 67. DisablingAutomatic 172.16.0.0/16Summarization 172.16.0.0/16R3# show ip route<output omitted>D 172.16.3.0/30 [90/41024000] via 192.168.10.5, 00:00:12, S0/0/0 [90/41024000] via 192.168.10.9, 00:00:12, S0/0/1 The slowest link is the 64-Kbps link 67
    68. 68. Manual Summarization EIGRP can be configured to summarize routes, whether or not automatic summarization (auto-summary) is enabled. Modified topology. 68
    69. 69. ManualSummarizationR3(config)# interface loopback 2R3(config-if)# ip address 192.168.2.1 255.255.255.0R3(config-if)# interface loopback 3R3(config-if)# ip address 192.168.3.1 255.255.255.0R3(config-if)# router eigrp 1R3(config-router)# network 192.168.2.0R3(config-router)# network 192.168.3.0 Add two more networks to R3. Configure EIGRP network statements. 69
    70. 70. ManualSummarization 192.168.1.0/24, 192.168.2.0/24, 192.168.3.0/24 192.168.1.0/24, 192.168.2.0/24, 192.168.3.0/24Only pertinent routes shownR1# show ip routeD 192.168.1.0/24 [90/2172416] via 192.168.10.6, 02:07:38, S0/0/1D 192.168.2.0/24 [90/2297856] via 192.168.10.6, 00:00:34, S0/0/1D 192.168.3.0/24 [90/2297856] via 192.168.10.6, 00:00:18, S0/0/1R2# show ip routeD 192.168.1.0/24 [90/3014400] via 192.168.10.10, 02:08:50, S0/0/1D 192.168.2.0/24 [90/3139840] via 192.168.10.10, 00:01:46, S0/0/1D 192.168.3.0/24 [90/3139840] via 192.168.10.10, 00:01:30, S0/0/1 Instead of sending three separate networks, R3 can summarize the 192.168.1.0/24, 192.168.2.0/24, and 192.168.3.0/24 networks as a single route. 70
    71. 71. Determining the Summary EIGRP Route1. Write out the networks that you want to summarize in binary.2. Find the matching bits.  Count the number of leftmost matching bits, which in this example is 22.  This number becomes your subnet mask for the summarized route: /22 or 255.255.252.0.3. To find the network address for summarization, copy the matching 22 bits and add all 0 bits to the end to make 32 bits.The result is the summary network address and mask for 192.168.0.0/22 71
    72. 72. Configure EIGRP Manual 192.168.0.0/22 Summarization 192.168.0.0/22Router(config-if)# ip summary-address eigrp as-number network-address subnet-maskR3(config)# interface serial 0/0/0R3(config-if)# ip summary-address eigrp 1 192.168.0.0 255.255.252.0R3(config)# interface serial 0/0/1R3(config-if)# ip summary-address eigrp 1 192.168.0.0 255.255.252.0R3# show ip route Creates a Null0 summary route<output omitted>D 192.168.0.0/22 is a summary, 00:00:06, Null0  Because R3 has two EIGRP neighbors, the EIGRP manual summarization in configured on both Serial 0/0/0 and Serial 0/0/1. 72
    73. 73. Verify EIGRPManual 192.168.0.0/22Summarization 192.168.0.0/22R1# show ip route<output omitted>D 192.168.0.0/22 [90/2172416] via 192.168.10.6, 00:01:11, Serial0/0/1R2# show ip route<output omitted>D 192.168.0.0/22 [90/3014400] via 192.168.10.10, 00:00:23, Serial0/0/1 Fewer number of total routes in routing tables  Faster routing table lookup process more efficient. Summary routes also require less bandwidth  Single route can be sent rather than multiple individual routes. 73
    74. 74. Redistribute EIGRP Default Default Route default static route in Route EIGRP updatesThe ISP router in our topology doesnot physically exist. By using aloopback interface, we can simulatea connection to another router. R2(config)# ip route 0.0.0.0 0.0.0.0 loopback 1 R2(config)# router eigrp 1 R2(config-router)# redistribute static 74
    75. 75. RedistributeEIGRP Default Default Route default static route inRoute EIGRP updatesOnly static default route shown,other output omitted.R1# show ip routeGateway of last resort is 192.168.10.6 to network 0.0.0.0D*EX 0.0.0.0/0 [170/3651840] via 192.168.10.6, 00:02:14, S0/0/1R2# show ip routeGateway of last resort is 0.0.0.0 to network 0.0.0.0S* 0.0.0.0/0 is directly connected, Loopback1R3# show ip routeGateway of last resort is 192.168.10.9 to network 0.0.0.0D*EX 75 0.0.0.0/0 [170/3139840] via 192.168.10.9, 00:01:25, S0/0/1
    76. 76. RedistributeEIGRP Default Default Route default static route inRoute EIGRP updatesOnly static default route shown,other output omitted.R1# show ip routeGateway of last resort is 192.168.10.6 to network 0.0.0.0D*EX 0.0.0.0/0 [170/3651840] via 192.168.10.6, 00:02:14, S0/0/1 D: This static route was learned from an EIGRP routing update. *: The route is a candidate for a default route. EX: The route is an external EIGRP route, in this case a static route outside of the EIGRP routing domain. 170: This is the AD of an external EIGRP route. 76
    77. 77. EIGRP Default Route Redistribute Default Route default static route in EIGRP updates There is another method to propagate a default route in EIGRP, using the ip default-network command. More information on this command can be found at this site:  http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0 080094374.shtml. 77
    78. 78. CIS 185 Advanced Routing Protocols EIGRP Part 2 Rick Graziani Cabrillo College graziani@cabrillo.edu Last Updated: Fall 2009

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