CO5023 EIGRP

Features of EIGRP EIGRP is a highly advanced distanced vector routing protocol Uses Protocol dependent modules to route different packets across the same physical infrastructure (v. useful for ipv4 and ipv6) Has its own reliable transport protocol (RTP), as it cannot rely on TCP for transport Includes both reliable and unreliable delivery Uses partial and bounded updates: as far as possible sends only the updated information to routers affected when a topology changes. Also supports load balancing among unequal cost routes

EIGRP Packet Types Hello packets - Used for discovery and maintanance of neighbor adjacencies. Sent every 5 seconds (60s NBMA) Sent with unreliable delivery Multicast (on most network types) Update packets - Propagates routing information to EIGRP neighbors. Sent only when necessary. Sent with reliable delivery Unicast or multicast Acknowledgment packets - Used to acknowledge the receipt of an EIGRP message that was sent using reliable delivery. Sent with unreliable delivery Unicast Query packets - Used to query routes from neighbors when connectivity to a network is lost (network placed in active state). Sent with reliable delivery Unicast or multicast Reply packets - Sent in response to a query. Sent with reliable delivery Unicast

Configuring EIGRP EIGRP configuration is much like other routing protocols. router eigrp AS-number network x.x.x.x The autonomous system (AS) number is a bit like the process ID in OSPF. Notice the network command does not need a wildcard mask. EIGRP will be enabled on all interfaces within the classful range (if this behaviour is not desired, a wildcard mask can be used)

Multi-area routing table O - Router (type 1) and network (type 2) LSAs describe the details within an area (intra-area). O IA - When an ABR receives summary LSAs, it adds them to its LSDB and regenerates them into the local area. Summary LSAs appear in the routing table as IA (inter-area routes). O E1 or O E2 - External LSAs appear in the routing table marked as external type 1 (E1) or external type 2 (E2) routes. The SPF calculation starts with intra-area routes, then inter-area, then external.

Verifying EIGRP

EIGRP Operation Initial route discovery… 1.Swap hello packets to create neighbour adjacency 2.Then they send each other all of their routing information (using split horizon: routing information learned from a particular interface is never sent back out through that interface – prevents routing loops) 3.Routers update their tables accordingly, reaching a state of convergence.

EIFRP Metrics EIGRP metrics appear to cover everything we could possibly want… Bandwidth (= /bandwidth) Load Delay Reliability However, the delay and load aren’t updated in real time by any form of network monitoring – they are static estimates of these values. If you want a routing protocol which actually attempts to monitor and maintain these things dynamically, try ant colony optimisation. You can adjust the EIGRP metric by changing its k values A zero k value means the corresponding metric value is ignored When calculating the metric for a route, EIGRP uses the slowest bandwidth and sums the delays

Diffuse Update Algorithm (DUAL) Terminology Successor – next hop on shortest route Feasible distance – distance through successor Feasible successor – next hop on alternative route Reported distance – feasible distance from neighbour Feasibility condition: used to identify feasible successors In the event that a route fails, DUAL will promote the feasible successor with shortest reported distance to be the successor. A backup route is a feasible successor if it meets the feasibility condition: If the reported distance from the neighbour is less than the local router’s feasible distance, then the feasibility condition is met This ensures that no routing loops are present in the network

DUAL convergence If a route fails and no feasible successor is available for the destination network, DUAL places the route into an active state. It is then necessary to send out query packets asking neighbours for routes to the destination. You can observe DUAL’s activity at the command line by using the privileged mode command: debug eigrp fsm