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  1. 1. Basics of Dynamic Routing Presented by Aaron Jarvis Network Engineer
  2. 2. Agenda <ul><li>Introduction to Dynamic Routing </li></ul><ul><li>Choosing the Right Protocol </li></ul><ul><li>Configuring Dynamic Routing </li></ul><ul><li>How the ITaP Production Data Network uses dynamic routing </li></ul>
  3. 3. Agenda <ul><li>Introduction to Dynamic Routing </li></ul><ul><li>Choosing the Right Protocol </li></ul><ul><li>Configuring Dynamic Routing </li></ul><ul><li>How the ITaP Production Data Network uses dynamic routing </li></ul>
  4. 4. Introduction to Dynamic Routing <ul><li>What is routing? </li></ul><ul><ul><li>How data is forwarded between subnets </li></ul></ul><ul><ul><li>Network Layer or Layer 3 in the OSI Model </li></ul></ul><ul><ul><li>Provides end-to-end reachability </li></ul></ul>
  5. 5. Introduction to Dynamic Routing <ul><li>How are routing decisions made? </li></ul><ul><ul><li>Forwarded based on the destination IP address </li></ul></ul><ul><ul><li>Router builds/maintains a routing table </li></ul></ul><ul><ul><ul><li>Current view of the network </li></ul></ul></ul><ul><ul><ul><li>Populated either dynamically or manually </li></ul></ul></ul>router#show ip route Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route Gateway of last resort is 192.5.40.54 to network 0.0.0.0 69.0.0.0/19 is subnetted, 1 subnets O E2 69.51.160.0 [110/1] via 192.5.40.54, 6d21h, Port-channel61 O E2 199.233.104.0/24 [110/1] via 192.5.40.54, 3w4d, Port-channel61 192.5.40.0/24 is variably subnetted, 19 subnets, 4 masks D 192.5.40.238/32 [90/131328] via 192.31.0.13, 2d16h, Vlan4094 [90/131328] via 192.31.0.113, 2d16h, Vlan4084 O IA 192.5.40.225/32 [110/2] via 192.5.40.54, 3w4d, Port-channel61 O IA 192.5.40.227/32 [110/4] via 192.5.40.54, 3w4d, Port-channel61 C 192.5.40.240/28 is directly connected, Vlan898 D 192.5.40.168/29 [90/3072] via 192.31.0.113, 7w0d, Vlan4084 [90/3072] via 192.31.0.13, 7w0d, Vlan4094 Snip……
  6. 6. Agenda <ul><li>Introduction to Dynamic Routing </li></ul><ul><li>Choosing the Right Protocol </li></ul><ul><li>Configuring Dynamic Routing </li></ul><ul><li>How the ITaP Production Data Network uses dynamic routing </li></ul>
  7. 7. Choosing the Right Protocol <ul><li>Interior Routing Protocols </li></ul><ul><ul><li>Used within an autonomous system </li></ul></ul><ul><ul><li>Used within an area of administrative control </li></ul></ul><ul><li>Exterior Routing Protocols </li></ul><ul><ul><li>Used between autonomous systems </li></ul></ul><ul><ul><li>Used to peer with networks in which you have no administrative control </li></ul></ul>
  8. 8. Choosing the Right Protocol <ul><li>Interior Routing Protocols </li></ul><ul><ul><li>Static </li></ul></ul><ul><ul><li>RIP </li></ul></ul><ul><ul><li>OSPF </li></ul></ul><ul><ul><li>EIGRP </li></ul></ul><ul><ul><li>ISIS </li></ul></ul><ul><li>Exterior Routing Protocols </li></ul><ul><ul><li>BGP </li></ul></ul><ul><li>NOTE: This is not an exhaustive list of protocols available but merely a list of those commonly used. </li></ul>
  9. 9. Choosing the Right Protocol <ul><li>Static Routing </li></ul><ul><ul><li>May be suitable on small networks </li></ul></ul><ul><ul><li>Administration intensive as changes have to be made on each router </li></ul></ul><ul><ul><li>Commonly used for default routing </li></ul></ul><ul><ul><ul><li>0.0.0.0/0  Next Hop Router </li></ul></ul></ul>
  10. 10. Choosing the Right Protocol <ul><li>Dynamic Routing Protocol Types </li></ul><ul><ul><li>Distance Vector </li></ul></ul><ul><ul><ul><li>Routing Information Protocol(RIP) </li></ul></ul></ul><ul><ul><ul><li>Interior Gateway Routing Protocol(IGRP) </li></ul></ul></ul><ul><ul><ul><li>Enhanced Interior Gateway Routing Protocol(EIGRP) </li></ul></ul></ul><ul><ul><li>Link State </li></ul></ul><ul><ul><ul><li>Open Shortest Path First(OSPF) </li></ul></ul></ul><ul><ul><ul><li>Intermediate System to Intermediate System(ISIS) </li></ul></ul></ul><ul><ul><li>Path Vector </li></ul></ul><ul><ul><ul><li>Border Gateway Protocol(BGP) </li></ul></ul></ul>
  11. 11. Choosing the Right Protocol <ul><li>Routing Information Protocol(RIP) </li></ul><ul><ul><li>RFC 1058(RIPv1), 1988 </li></ul></ul><ul><ul><ul><li>Classful, no support for VLSM </li></ul></ul></ul><ul><ul><ul><li>No support for authentication </li></ul></ul></ul><ul><ul><li>RFC 2453(RIPv2), 1998 </li></ul></ul><ul><ul><ul><li>Classless, support for CIDR </li></ul></ul></ul><ul><ul><ul><li>Support for authentication </li></ul></ul></ul><ul><ul><li>Uses hop count as routing metric </li></ul></ul><ul><ul><li>Slow to converge </li></ul></ul><ul><ul><li>Not very scalable </li></ul></ul><ul><ul><ul><li>Limited to 15 hops </li></ul></ul></ul>
  12. 12. Choosing the Right Protocol <ul><li>Interior Gateway Routing Protocol(IGRP) </li></ul><ul><ul><li>Invented by Cisco to overcome limitations of RIP </li></ul></ul><ul><ul><li>Allows for hop count up to 255 </li></ul></ul><ul><ul><li>Allows for multiple route metrics </li></ul></ul><ul><ul><ul><li>Bandwidth </li></ul></ul></ul><ul><ul><ul><li>Delay </li></ul></ul></ul><ul><ul><ul><li>Load </li></ul></ul></ul><ul><ul><ul><li>MTU </li></ul></ul></ul><ul><ul><ul><li>Reliability </li></ul></ul></ul><ul><ul><li>Classful, no support for VLSM </li></ul></ul>
  13. 13. Choosing the Right Protocol <ul><li>Enhanced Interior Gateway Routing Protocol(EIGRP) </li></ul><ul><ul><li>Replaced IGRP </li></ul></ul><ul><ul><li>Maintains a Topology table </li></ul></ul><ul><ul><ul><li>Successors, feasible successors </li></ul></ul></ul><ul><ul><li>Allows for multiple route metrics </li></ul></ul><ul><ul><li>Classless, support for CIDR </li></ul></ul><ul><ul><li>Very fast to converge </li></ul></ul><ul><ul><li>Maintains neighbor relationships </li></ul></ul><ul><ul><li>Diffusing Update Algorithm(DUAL) </li></ul></ul><ul><ul><li>Not as CPU intensive as OSPF </li></ul></ul>
  14. 14. Choosing the Right Protocol <ul><li>Open Shortest Path First(OSPF) </li></ul><ul><ul><li>RFC 2328(OSPFv2), 1998 </li></ul></ul><ul><ul><li>Maintains neighbor relationships </li></ul></ul><ul><ul><li>Concept of Areas </li></ul></ul><ul><ul><ul><li>Different areas can be used to control flooding of routing information </li></ul></ul></ul><ul><ul><li>Classless, supports VLSM </li></ul></ul><ul><ul><li>Fast to converge </li></ul></ul><ul><ul><li>CPU Intensive Dijkstra Algorithm </li></ul></ul><ul><ul><li>Designing can be complicated </li></ul></ul>
  15. 15. Choosing the Right Protocol <ul><li>Intermediate System to Intermediate System(ISIS) </li></ul><ul><ul><li>RFC 1142, 1990 </li></ul></ul><ul><ul><li>Dijkstra Algorithm </li></ul></ul><ul><ul><li>Mainly used by large service providers </li></ul></ul><ul><ul><li>Does not use IP to carry routing information </li></ul></ul><ul><ul><ul><li>Uses ISO addresses </li></ul></ul></ul><ul><ul><li>Level Concept </li></ul></ul><ul><ul><ul><li>Level 1 or Intra Area </li></ul></ul></ul><ul><ul><ul><li>Level 2 or Inter Area </li></ul></ul></ul><ul><ul><ul><li>Level 1/2 or Both </li></ul></ul></ul><ul><ul><li>Classless, supports VLSM </li></ul></ul>
  16. 16. Choosing the Right Protocol <ul><li>Border Gateway Protocol(BGP) </li></ul><ul><ul><li>RFC 4271(BGPv4), 2006 </li></ul></ul><ul><ul><li>Peers manually defined </li></ul></ul><ul><ul><li>Used typically for multi-homing to ISP(s) </li></ul></ul><ul><ul><li>Very scalable </li></ul></ul><ul><ul><li>Makes decisions based upon AS Path </li></ul></ul><ul><ul><li>Lots of policy options </li></ul></ul><ul><ul><li>Very granular control </li></ul></ul>
  17. 17. Agenda <ul><li>Introduction to Dynamic Routing </li></ul><ul><li>Choosing the Right Protocol </li></ul><ul><li>Configuring Dynamic Routing </li></ul><ul><li>How the ITaP Production Data Network uses dynamic routing </li></ul>
  18. 18. Configuring Dynamic Routing <ul><li>How to configure dynamic routing? </li></ul><ul><ul><li>Choose a protocol that meets your needs </li></ul></ul><ul><ul><li>Each vendor has specific commands but should have a configuration guide available to assist </li></ul></ul><ul><ul><li>Plan well to ensure a functional network </li></ul></ul><ul><ul><ul><li>Create a diagram </li></ul></ul></ul><ul><ul><ul><li>Consider high availability technologies </li></ul></ul></ul><ul><ul><ul><ul><li>HSRP </li></ul></ul></ul></ul><ul><ul><ul><ul><li>VRRP </li></ul></ul></ul></ul>
  19. 19. Configuring Dynamic Routing <ul><li>Best Practices </li></ul><ul><ul><li>Only enable a routing protocol for interfaces you intend on using </li></ul></ul><ul><ul><ul><li>If compromised can cause a lot of problems </li></ul></ul></ul><ul><ul><li>Enable authentication(if available) </li></ul></ul><ul><ul><ul><li>Use authentication to ensure that the remote routers are valid peers </li></ul></ul></ul>
  20. 20. Configuring Dynamic Routing <ul><li>Best Practices Cont… </li></ul><ul><ul><li>Control Network Advertisements </li></ul></ul><ul><ul><ul><li>Only allow networks to be advertised that should be </li></ul></ul></ul><ul><ul><li>Private Address Space </li></ul></ul><ul><ul><ul><li>Use only within your organization </li></ul></ul></ul><ul><ul><li>Private AS Numbers </li></ul></ul><ul><ul><ul><li>Strip before sending to ISP </li></ul></ul></ul>
  21. 21. Agenda <ul><li>Introduction to Dynamic Routing </li></ul><ul><li>Choosing the Right Protocol </li></ul><ul><li>Configuring Dynamic Routing </li></ul><ul><li>How the ITaP Production Data Network uses dynamic routing </li></ul>
  22. 22. How the ITaP Production Network Uses Dynamic Routing <ul><li>Routing Protocols Used </li></ul><ul><ul><li>Interior </li></ul></ul><ul><ul><ul><li>EIGRP </li></ul></ul></ul><ul><ul><ul><li>OSPF </li></ul></ul></ul><ul><ul><ul><li>Static </li></ul></ul></ul><ul><ul><li>Exterior </li></ul></ul><ul><ul><ul><li>BGP </li></ul></ul></ul>
  23. 23. How the ITaP Production Network Uses Dynamic Routing <ul><li>Whiteboard Drawing </li></ul>
  24. 24. <ul><li>Questions? </li></ul>

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