IPv6 Static Routes

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  • In order for Branch-1 to forward a packet to Branch-2’s LANs, it has to send the packet out of its serial 0/0/1 interface. The exit interface is also considered the direction in which to reach these networks.
  • Using the exit interface displays the static route as being directly connected, hence the name Directly connected static route. Read the “L” on the slide. Explain how the link shows a 128 bit prefix and the “C” displays the actual prefix used. In this example, the subnet identified by the “C” is the 2001:DB8:A::2/127 and the address configured on the interface identified by the “L” or local host route is 2001:DB8:A::3/128
  • In this example, in order for Branch-1 to forward a packet to Branch-2’s LANs it must forward the packet to the next hop router in the direction of those networks. In this example, that would be the IPv6 address of Branch-2.
  • There is a noticeable difference how a directly connected and a recursive static route are displayed in the routing table. A directly connected static route shows that it is directly connected to an interface, while the recursive static route shows via the next hop router identified by its IPv6 address. In this example, in order for Branch-1 to route traffic to Brnach-2’s LANs, it will send it to the 2001:DB8:A::2 address which happens to be the IPv6 address configured on Branch-2. Now the router has to do a second routing table lookup to determine how to get to the 2001:DB8:A::2 network. Based on this information, the router will now forward the packet out of its serial 0/0/1 interface.
  • Fully specified static routes displays both the next hop router’s IPv6 address as well as the exit interface.
  • Fully specified static routes displays both the next hop router’s IPv6 address as well as the exit interface. As you can see in the routing table, a fully specified static route displays both the next hop router’s IPv6 address as well as the exit interface.
  • A default route is used when no other routes in the routing table match the packet destination IP address. In other words, when a more specific match does not exist. A default route is usually configured on a company's edge router that connects to the ISP’s network. The command for an IPv6 default route is ::/0. This is the IPv6 version of the all zero address (remember the :: is used to identify consecutive zeros) which is similar to the quad zero address used in an IPv4 default route. A default route can be configured as a directly connected, recursive, or as a fully specified static default route.
  • Notice how the default route is displayed in the routing table as an “S” because the correct name is a static default route but notice that the * (asterisk) is not used to identify a default route in an IPv6 routing table.
  • Notice how we can ping both LAN interfaces with only one static route entry in the routing table. Instead of configuring two static routes to reach Branch-2’s LANs, we can summarize them based on common bits in the network portion of the address. In this example, both addresses have the first 46-bits in common. 16 bits in the first two hextets and 14 bits in the 3rdhextet for a total of 63-bits. As you can see, we can ping each LAN interface with only one static route entry in the routing table.
  • Some of the output was omitted because it didn’t fit on the slide. 5 floating static routes were configured with an administrative distance of 91, one more that the routing protocol which in this case is EIGRP. The output to the left displays the IPv6 routing table with only the dynamic routes installed. When the primary path (interface s0/0/0) goes down, the dynamic routes are removed from the routing table and the floating static routes replace them. The Branch-1 will now route traffic to Branch-2 through the backup path (Serial 0/0/1).
  • IPv6 Static Routes

    1. 1. IPv6 Static Routes John Rullan Cisco Certified Instructor Trainer Thomas A. Edison CTE HS Stephen Lynch Network Architect, CCIE #36243 ABS Technology Architects
    2. 2. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 2 • Static routes defines explicit path between two routers. They are not automatically updated which means you must manually reconfigure static routes when network changes occur. • Static routes use less bandwidth than dynamic routes. • No CPU cycles are used to calculate and analyze routing updates. • Static routes should be used in an environments where network traffic is predictable and where the network design is simple. • Static routes should not be used in a large network environment where it’s constantly changing because static routes cannot react to network changes. • Even though static routes are obsolete due to the high use of dynamic routes in a network, some companies still implement static routes for special occasions. • Static routes are also useful for specifying a gateway of last resort (a default route which all un-routeable packets are sent).
    3. 3. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 3 There are four types of static routes. The following types of IPv4 and IPv6 static routes will be discussed: • Standard static route • Default static route • Summary static route • Floating static route
    4. 4. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 4 • You must specify only the output interface (the interface on which all packets are sent to the destination network) in a directly connected static route. • The router assumes the destination is directly attached to the output interface. Directly Connected Branch-2 2001:DB8:A::2/127 2001:DB8:A::3/127 2001:DB8:2::1/64 2001:DB8:3::1/64 S0/0/0 S0/0/1 InternetS0/0/0 Branch-1 LAN-1 LAN-2 Branch-1(config)# ipv6 route 2001:DB8:2::1/64 s0/0/1 Branch-1(config)# ipv6 route 2001:DB8:3::1/64 s0/0/1 Directly Connected
    5. 5. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 5 Branch-2 2001:DB8:A::2/127 2001:DB8:A::3/127 2001:DB8:2::1/64 2001:DB8:3::1/64 Branch-1(config)# ipv6 route 2001:DB8:2::1/64 s0/0/1 Branch-1(config)# ipv6 route 2001:DB8:3::1/64 s0/0/1 S0/0/0 S0/0/1 InternetS0/0/0 Branch-1 Directly Connected LAN-1 LAN-2 Branch-1#show ipv6 route (Output Omitted) S 2001:DB8:2::/62 [1/0] via ::, Serial0/0/1 S 2001:DB8:3::/62 [1/0] via ::, Serial0/0/1 C 2001:DB8:A::2/127 [0/0] via ::, Serial0/0/1 L 2001:DB8:A::3/128 [0/0] via ::, Serial0/0/1 C 2001:DB8:B::/127 [0/0] via ::, Serial0/0/0 L 2001:DB8:B::/128 [0/0] via ::, Serial0/0/0 L FF00::/8 [0/0] via ::, Null0 Branch-2# “L” in the routing table is a new identifier which indicates the specific address assigned to an interface, as opposed to “C” which only displays the subnet.
    6. 6. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 6 • In a next-hop static route, the IPv6 address of the neighboring router is specified. • The output interface is derived from the next hop. • Before any packet is forwarded by router, the routing table process must determine the exit interface to use to in order to forward the packet. This causes the router to take a second look at the routing table to determine the exit interface for the destination network. Branch-2 2001:DB8:A::2/127 2001:DB8:A::3/127 2001:DB8:2::1/64 2001:DB8:3::1/64 S0/0/0 S0/0/1 InternetS0/0/0 Branch-1 LAN-1 LAN-2 Next Hop/Recursive Branch-1(config)# ipv6 route 2001:DB8:2::1/64 2001:DB8:A::2 Branch-1(config)# ipv6 route 2001:DB8:3::1/64 2001:DB8:A::2
    7. 7. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 7 Branch-1(config)# ipv6 route 2001:DB8:2::1/64 2001:DB8:A::2 Branch-1(config)# ipv6 route 2001:DB8:3::1/64 2001:DB8:A::2 Next Hop/Recursive Branch-1#show ipv6 route (Output Omitted) S 2001:DB8:2::/64 [1/0] via 2001:DB8:A::2 S 2001:DB8:3::/64 [1/0] via 2001:DB8:A::2 C 2001:DB8:A::2/127 [0/0] via ::, Serial0/0/1 L 2001:DB8:A::3/128 [0/0] via ::, Serial0/0/1 C 2001:DB8:B::/127 [0/0] via ::, Serial0/0/0 L 2001:DB8:B::/128 [0/0] via ::, Serial0/0/0 L FF00::/8 [0/0] via ::, Null0 Branch-2# Branch-2 2001:DB8:A::2/127 2001:DB8:A::3/127 2001:DB8:2::1/64 2001:DB8:3::1/64 S0/0/0 S0/0/1 InternetS0/0/0 Branch-1 LAN-1 LAN-2
    8. 8. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 8 Branch-2 2001:DB8:A::2/64 2001:DB8:A::1/64 2001:DB8:2::1/64 2001:DB8:3::1/64 G0/0 G0/0 Branch-1 LAN-1 LAN-2 Branch-1(config)# ipv6 route 2001:DB8:2::1/64 g0/0 2001:DB8:A::2 Branch-1(config)# ipv6 route 2001:DB8:3::1/64 g0/0 2001:DB8:A::2Fully Specified • The output interface and the next-hop address are both used in a fully specify static route. • Used when the output interface is a multi-access interface and needs the next-hop address to be identified. • The next-hop must be directly attached to the specified output interface. G0/0 G0/0 Branch-4 Branch-3 2001:DB8:A::4/64 2001:DB8:A::3/64 DSW-1 G0/1 G0/0
    9. 9. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 9 Fully Specified Branch-1#show ipv6 route (Output Omitted) S 2001:DB8:2::1/64 [1/0] via 2001:DB8:A::2, Gigabit0/0 S 2001:DB8:3::1/64 [1/0] via 2001:DB8:A::2, Gigabit0/0 C 2001:DB8:A::2/127 [0/0] via ::, Serial0/0/1 L 2001:DB8:A::3/128 [0/0] via ::, Serial0/0/1 C 2001:DB8:B::/127 [0/0] via ::, Serial0/0/0 L 2001:DB8:B::/128 [0/0] via ::, Serial0/0/0 L FF00::/8 [0/0] via ::, Null0 Branch-2# Branch-2 2001:DB8:A::2/64 2001:DB8:A::1/64 2001:DB8:2::1/64 2001:DB8:3::1/64 G0/0 G0/0 Branch-1 LAN-1 LAN-2 G0/0 G0/0 Branch-4 Branch-3 2001:DB8:A::4/64 2001:DB8:A::3/64 DSW-1 G0/1 G0/0
    10. 10. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 10 • No other routes in the routing table match the packet destination IP address. In other words, when a more specific match does not exist. • A common use is when connecting a company's edge router to the ISP’s network. Branch-2 2001:DB8:A::2/127 2001:DB8:A::3/127 2001:DB8:2::1/64 S0/0/0 S0/0/1 InternetS0/0/0 Branch-1 LAN-1 LAN-2 Branch-1(config)#ipv6 route ::/0 s0/0/0 Branch-1(config)#ipv6 route ::/0 2001:DB8:A::2 Branch-1(config)#ipv6 route ::/0 s0/0/0 2001:DB8:A::2 2001:DB8:3::1/64
    11. 11. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 11 Branch-2 2001:DB8:A::2/127 2001:DB8:A::3/127 2001:DB8:2::1/64 2001:DB8:3::1/64 S0/0/0 S0/0/1 InternetS0/0/0 Branch-1 LAN-1 LAN-2 Branch-1(config)#ipv6 route ::/0 s0/0/0 Branch-1#sh ipv6 route (Output Omitted) S ::/0 [1/0] via ::, Serial0/0/0 S 2001:DB8:2::1/64 [1/0] via 2001:DB8:A::2, Serial0/0/1 S 2001:DB8:3::1/64 [1/0] via 2001:DB8:A::2, Serial0/0/1 C 2001:DB8:A::2/127 [0/0] via ::, Serial0/0/1 L 2001:DB8:A::3/128 [0/0] via ::, Serial0/0/1 C 2001:DB8:B::/127 [0/0] via ::, Serial0/0/0 L 2001:DB8:B::/128 [0/0] via ::, Serial0/0/0 L FF00::/8 [0/0] via ::, Null0 Branch-1# Default Route
    12. 12. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 12 • Summary routes are used to reduce the number of routing table entries. • Multiple static routes can be summarized into a single static route if: - The destination networks are contiguous and can be summarized into a single network address. - The multiple static routes all use the same exit interface or next-hop IP address. Branch-2 2001:DB8:A::2/127 2001:DB8:A::3/127 2001:DB8:2::1/64 S0/0/0 S0/0/1 InternetS0/0/0 Branch-1 LAN-1 LAN-2 2001:DB8:3::1/64
    13. 13. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 13 Branch-1(config)#ipv6 route 2001:DB8:2::/46 s0/0/0 Branch-1#show ipv6 route (output omitted) S ::/0 [1/0] via ::, Serial0/0/0 S 2001:DB8::/46 [1/0] via ::, Serial0/0/1 2001:DB8:0000000000000010 2001:DB8:0000000000000011 Summarize based on common bits: • 16-bits in the 1st and 2nd hextets for a total of 32-bits • 14-bits in the 3rd hextet • Total of 46-bits in common between the two addresses Common Bits Branch-1# ping 2001:db8:2::1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2001:db8:2::, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/10/41 ms Branch-1# ping 2001:db8:3::1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2001:db8:3::, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 2/9/18 ms Branch-1# Branch-2 2001:DB8:A::2/127 2001:DB8:A::3/127 2001:DB8:2::/64 S0/0/0 S0/0/1 InternetS0/0/0 Branch-1 LAN-1 LAN-2 2001:DB8:3::/64
    14. 14. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 14 • A floating static route is a static route that the router uses to back up dynamic route. • You must configure a floating static route with a higher administrative distance than the dynamic route that it backs up. • In this instance, the router prefers a dynamic route to a floating static route. You can use a floating static route as a replacement if the dynamic route is lost. InternetBranch-1 Branch-2
    15. 15. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Public 15 InternetBranch-1 Branch-2 Branch-1(config)# ipv6 route 2001:DB8:4::1/127 s0/0/1 91 Branch-1(config)# ipv6 route 2001:DB8:5::1/127 s0/0/1 91 Branch-1(config)# ipv6 route 2001:DB8:6::1/127 s0/0/1 91 Branch-1(config)# ipv6 route 2001:DB8:C::1/127 s0/0/1 91 Branch-1(config)# ipv6 route 2001:DB8:A::1/127 s0/0/1 91 Branch-1#sh ipv6 route (output omitted) D 2001:DB8:4::/128 [90/3321856] via FE80::2E0:8FFF:FE31:4201, Serial0/0/0 D 2001:DB8:5::/128 [90/3321856] via FE80::2E0:8FFF:FE31:4201, Serial0/0/0 D 2001:DB8:6::/128 [90/3321856] via FE80::2E0:8FFF:FE31:4201, Serial0/0/0 D 2001:DB8:B::/127 [90/3193856] via FE80::2E0:8FFF:FE31:4201, Serial0/0/0 D 2001:DB8:C::/127 [90/2681856] via FE80::2E0:8FFF:FE31:4201, Serial0/0/0 Branch-1# Branch-1#show ipv6 route (output omitted) S 2001:DB8:4::/128 [91/0] via ::, Serial0/0/1 S 2001:DB8:5::/128 [91/0] via ::, Serial0/0/1 S 2001:DB8:6::/128 [91/0] via ::, Serial0/0/1 S 2001:DB8:A::/128 [91/0] via ::, Serial0/0/1 S 2001:DB8:C::/128 [91/0] Branch-1#
    16. 16. Thank you.

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