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Basics of Dynamic Routing

Basics of Dynamic Routing. Presented by Aaron Jarvis Network Engineer. Agenda. Introduction to Dynamic Routing Choosing the Right Protocol Configuring Dynamic Routing How the ITaP Production Data Network uses dynamic routing. Agenda. Introduction to Dynamic Routing

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Basics of Dynamic Routing

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  1. Basics of Dynamic Routing Presented by Aaron Jarvis Network Engineer

  2. Agenda Introduction to Dynamic Routing Choosing the Right Protocol Configuring Dynamic Routing How the ITaP Production Data Network uses dynamic routing

  3. Agenda Introduction to Dynamic Routing Choosing the Right Protocol Configuring Dynamic Routing How the ITaP Production Data Network uses dynamic routing

  4. Network • What is routing? • How data is forwarded between subnets • Network Layer or Layer 3 in the OSI Model • Provides end-to-end reachability Data Link Introduction to Dynamic Routing Physical

  5. How are routing decisions made? • Forwarded based on the destination IP address • Router builds/maintains a routing table • Current view of the network • Populated either dynamically or manually Introduction to Dynamic Routing 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. Agenda Introduction to Dynamic Routing Choosing the Right Protocol Configuring Dynamic Routing How the ITaP Production Data Network uses dynamic routing

  7. Interior Routing Protocols • Used within an autonomous system • Used within an area of administrative control • Exterior Routing Protocols • Used between autonomous systems • Used to peer with networks in which you have no administrative control Choosing the Right Protocol

  8. Interior Routing Protocols • Static • RIP • OSPF • EIGRP • ISIS • Exterior Routing Protocols • BGP • NOTE: This is not an exhaustive list of protocols available but merely a list of those commonly used. Choosing the Right Protocol

  9. Static Routing • May be suitable on small networks • Administration intensive as changes have to be made on each router • Commonly used for default routing • 0.0.0.0/0  Next Hop Router Choosing the Right Protocol

  10. Dynamic Routing Protocol Types • Distance Vector • Routing Information Protocol(RIP) • Interior Gateway Routing Protocol(IGRP) • Enhanced Interior Gateway Routing Protocol(EIGRP) • Link State • Open Shortest Path First(OSPF) • Intermediate System to Intermediate System(ISIS) • Path Vector • Border Gateway Protocol(BGP) Choosing the Right Protocol

  11. Routing Information Protocol(RIP) • RFC 1058(RIPv1), 1988 • Classful, no support for VLSM • No support for authentication • RFC 2453(RIPv2), 1998 • Classless, support for CIDR • Support for authentication • Uses hop count as routing metric • Slow to converge • Not very scalable • Limited to 15 hops Choosing the Right Protocol

  12. Interior Gateway Routing Protocol(IGRP) • Invented by Cisco to overcome limitations of RIP • Allows for hop count up to 255 • Allows for multiple route metrics • Bandwidth • Delay • Load • MTU • Reliability • Classful, no support for VLSM Choosing the Right Protocol

  13. Enhanced Interior Gateway Routing Protocol(EIGRP) • Replaced IGRP • Maintains a Topology table • Successors, feasible successors • Allows for multiple route metrics • Classless, support for CIDR • Very fast to converge • Maintains neighbor relationships • Diffusing Update Algorithm(DUAL) • Not as CPU intensive as OSPF Choosing the Right Protocol

  14. Open Shortest Path First(OSPF) • RFC 2328(OSPFv2), 1998 • Maintains neighbor relationships • Concept of Areas • Different areas can be used to control flooding of routing information • Classless, supports VLSM • Fast to converge • CPU Intensive Dijkstra Algorithm • Designing can be complicated Choosing the Right Protocol

  15. Intermediate System to Intermediate System(ISIS) • RFC 1142, 1990 • Dijkstra Algorithm • Mainly used by large service providers • Does not use IP to carry routing information • Uses ISO addresses • Level Concept • Level 1 or Intra Area • Level 2 or Inter Area • Level 1/2 or Both • Classless, supports VLSM Choosing the Right Protocol

  16. Border Gateway Protocol(BGP) • RFC 4271(BGPv4), 2006 • Peers manually defined • Used typically for multi-homing to ISP(s) • Very scalable • Makes decisions based upon AS Path • Lots of policy options • Very granular control Choosing the Right Protocol

  17. Agenda Introduction to Dynamic Routing Choosing the Right Protocol Configuring Dynamic Routing How the ITaP Production Data Network uses dynamic routing

  18. How to configure dynamic routing? • Choose a protocol that meets your needs • Each vendor has specific commands but should have a configuration guide available to assist • Plan well to ensure a functional network • Create a diagram • Consider high availability technologies • HSRP • VRRP Configuring Dynamic Routing

  19. Best Practices • Only enable a routing protocol for interfaces you intend on using • If compromised can cause a lot of problems • Enable authentication(if available) • Use authentication to ensure that the remote routers are valid peers Configuring Dynamic Routing

  20. Best Practices Cont… • Control Network Advertisements • Only allow networks to be advertised that should be • Private Address Space • Use only within your organization • Private AS Numbers • Strip before sending to ISP Configuring Dynamic Routing

  21. Agenda Introduction to Dynamic Routing Choosing the Right Protocol Configuring Dynamic Routing How the ITaP Production Data Network uses dynamic routing

  22. Routing Protocols Used • Interior • EIGRP • OSPF • Static • Exterior • BGP How the ITaP Production Network Uses Dynamic Routing

  23. Whiteboard Drawing How the ITaP Production Network Uses Dynamic Routing

  24. Questions?

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