1 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 Choosing the Right Protocol Configuring Dynamic Routing How the ITaP Production Data Network uses dynamic routing

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

Introduction to Dynamic Routing 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 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 to network /19 is subnetted, 1 subnets O E [110/1] via , 6d21h, Port-channel61 O E /24 [110/1] via , 3w4d, Port-channel /24 is variably subnetted, 19 subnets, 4 masks D /32 [90/131328] via , 2d16h, Vlan4094 [90/131328] via , 2d16h, Vlan4084 O IA /32 [110/2] via , 3w4d, Port-channel61 O IA /32 [110/4] via , 3w4d, Port-channel61 C /28 is directly connected, Vlan898 D /29 [90/3072] via , 7w0d, Vlan4084 [90/3072] via , 7w0d, Vlan4094 Snip……

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

Choosing the Right Protocol 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 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 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  Next Hop Router

Choosing the Right Protocol 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 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 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 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 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 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 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

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

Configuring Dynamic Routing 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 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 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

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

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

How the ITaP Production Network Uses Dynamic Routing Whiteboard Drawing

Questions?