EIGRP

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EIGRP

• LSNDI RMRA
• MM Clements

2
Last Week

• OSPF requires more resources from router
• Fast convergence
• Less overhead good for large networks
• LSAs sent in LSUs only the changes are flooded
  to the network
• Supports VLSM
• Complex to configure!

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This week.

• EIGRP Cisco proprietary routing protocol
• Key features
• Neighbor and topology tables
• Feasible Distance Successor Routes
• EIGRP packet types
• Setting up EIGRP

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Enhanced Interior Gateway Protocol

• Released in 1994 as successor to IGRP
• Compatible with IGRP
• Hybrid routing protocol with best of distance
  vector link-state algorithms
• Uses partial updates and neighbour discovery
• Like OSPF but easier to configure
• Good for large multiprotocol networks that
  primarily use Cisco routers

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EIGRP

• Offers multiprotocol operation (IP, IPX etc)
• EIGRP multiplies IGRP metric by 256
• Uses 32-bit metric c.f. IGRP 24-bit metric
• Metric bandwidth/ delay
• EIGRP BW (107/ BW) x 256
• EIGRP delay (delay/10) x 256
• Max hop 224 c.f. IGRP 256

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EIGRP key features

• EIGRP automatically shares routing information
  with IGRP and vice versa
• EIGRP tags routes from other protocols as
  external
• Rapid convergence from Diffused Updating
  Algorithm (DUAL)
• Guaranteed no loops all routers running EIGRP
  update at the same time if change occurs
• Efficient use of BW partial incremental updates
  only
• Sent only to routers that need information not
  all routers

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Good use of Network Bandwidth

• Partial bounded updates, unlike OSPF
• No timed routing updates
• RIP 30s IGRP 90s full routing tables
• EIGRP uses small hello packets
• Unreliable no acknowledgements
• Supports VLSM CIDR unlike IGRP
• Uses PDMs to support IP, IPX, Appletalk

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EIGRP Router Tables

• Neighbour table lists adjacent routers
• One neighbour table per supported protocol
• Similar to OSPF adjacency database
• Holds neighbour address and interface data
• Hold time time to wait before considering
  neighbour to be down 3 x hello interval
• Multicast to 224.0.0.10
• Smooth Round Trip Timer SRTT

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Neighbour Table Contents

• Queue Count (Q Cnt) number of packets waiting
  in queue to be delivered
• If Q Cnt gt 0 means possible congestion problem
• Sequence number (Seq No) to keep track of
  neighbours transmissions (not hellos)
• Supports reliable, sequenced delivery of packets
  (like TCP) but using Reliable Transport Protocol
  (RTP)

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Neighbour Table
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Topology Table

• Made up of all EIGRP routing tables in AS
• DUAL takes data from neighbour and topology
  tables to calculate lowest cost routes
• Allows EIGRP to identify switch to alternative
  routes quickly
• Primary (successor) route placed in topology
  table
• Also keeps a backup route if available

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In Topology Table are

• Feasible Distance (FD) lowest calculated metric
  to each destination
• Route Source identifies number of router that
  identified the route originally
• Reported distance (RD) distance an adjacent
  router reports to a specific destination
• FD RD
• (2195458/ 281400)

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Also in Topology table.

• Interface information identifies the routers
  interface to reach a given destination
• Route status Passive (P) for a stable route
• Active (A) if DUAL is recalculating route
• Successor is primary route to destination
• Feasible successor is placed below successor as a
  backup route to be used when topology changes
  (saves total recalculation of routing)

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Successor Routes

• Appear in Topology and Routing table
• Can be up to 4 successor routes to a destination
• Can be of equal or unequal cost
• FS identified at same time as successors
• Only kept in Topology table
• Not mandatory to have FS
• If successor route goes down, lowest FS chosen

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Identifying Routes

• If no FS, router places Active status on a route
• Sends Query packets to all neighbours
• Neighbours reply with successor or no successor
• Passive status placed on route if positive reply
• DUAL always tries to identify a FS in case of
  problems saves querying neighbours and
  recalculations

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Neighbour Discovery and Rediscovery
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Reliable Transport Protocol

• RTP guarantees ordered delivery of routing
  packets using sequence numbers
• EIGRP is protocol independent doesnt need IP
• RTP used to multicast and unicast packets

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EIGRP Packet Types

• Hello sent on 1.544 Mbps or less every 60s
• Acknowledgement data-less hello packet
• Update sent to newly discovered neighbour
• Query multicast or unicast
• Reply response to a query

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Autonomous System Number

• An Autonomous System (AS) is a set of networks
  and routers under the control of one body
• This system has a common routing policy as
  presented to the Internet
• ASs are given unique numbers between 1 and 65535
• See RFC 1930

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Setting up EIGRP

• Needs Autonomous System Number
• Router(config)router eigrp 123
• Router(config-router)net 192.168.1.1 0.0.0.3
• Router(config-router)net 22.22.22.0 0.0.0.255
• Router(config-router)exit
• Uses Wildcard Mask

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Verifying EIGRP

• Routershow ip protocols
• This shows the routing protocol in use and other
  useful information too
• Routersh ip eigrp ?
• interfaces IP-EIGRP interfaces
• neighbors IP-EIGRP neighbors
• topology IP-EIGRP Topology Table
• traffic IP-EIGRP Traffic Statistics

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• Routersh ip pro
• Routing Protocol is "eigrp 123 "
• Outgoing update filter list for all interfaces
  is not set
• Incoming update filter list for all interfaces
  is not set
• Default networks flagged in outgoing updates
• Default networks accepted from incoming updates
  
• EIGRP metric weight K11, K20, K31, K40,
  K50
• EIGRP maximum hopcount 100
• EIGRP maximum metric variance 1
• Redistributing eigrp 123
• Automatic network summarization is in effect
• Automatic address summarization
• Maximum path 4
• Routing for Networks
• 192.168.1.0/30
• 22.22.22.0/24
• 192.168.1.12/30
• Routing Information Sources

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Debugging EIGRP

• Routerdebug eigrp ?
• fsm EIGRP Dual Finite State Machine
  events/actions
• packets EIGRP packets

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Debug output

• Routerdebug eigrp pa
• EIGRP Packets debugging is on
• (UPDATE, REQUEST, QUERY, REPLY, HELLO, ACK )
• Router
• EIGRP Received HELLO on Serial0/0/0 nbr
  192.168.1.2
• AS 123, Flags 0x0, Seq 26/0 idbQ 0/0
• EIGRP Received HELLO on Serial0/0/1 nbr
  192.168.1.6
• AS 123, Flags 0x0, Seq 20/0 idbQ 0/0
• EIGRP Sending HELLO on FastEthernet0/0
• AS 123, Flags 0x0, Seq 22/0 idbQ 0/0 iidbQ
  un/rely 0/0
• EIGRP Sending HELLO on Serial0/0/1
• AS 123, Flags 0x0, Seq 22/0 idbQ 0/0 iidbQ
  un/rely 0/0
• Remember to turn of debugging when you have
  finished
• undebug all will turn off all debugging processes

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Summary

• EIGRP similar to OSPF -
• Has neighbour table
• Sends hello packets
• Has topology table (1 for each protocol)
• Uses DUAL on Neighbour Topology tables
• Elects successors and feasible successors (FS)
• FS used in times of trouble fast selection
• Verification and debug commands