EIGRP

1
EIGRP

• Semester 5, Chapter 6
• Allan Johnson
• Modified by Sean He

2
Basics of EIGRP
3
EIGRP Metrics

• EIGRP scales IGRPs metrics by a factor of 256
• IGRP metric 24 bits EIGRP metric 32 bits
• Bandwidth and Delay are equally weighted
• Reliability, Load, and MTU are off by default
• Hop count limited to 224 (IGRPs limit is 255)
• To remember the metric components
• Big Bandwidth
• Dogs Delay
• Really Reliability
• Like Load
• Me MTU

4
EIGRP Tables

• Like OSPF, EIGRP maintains three unique tables to
  assist in routing traffic.
• Neighbor Table
• Topology Table
• Routing Table
• EIGRP maintains one table of each for each routed
  protocol configured on the router.
• For example, if a router was configured with IP,
  IPX and AppleTalk, EIGRP would maintain
• 3 Neighbor Tables
• 3 Topology Tables
• 3 Routing Tables

5
EIGRP Concepts

• Successor
• The best, least cost route to the destination
  installed in the routing table multiple
  successors can be installed for load balancing
• Feasible Successor
• A next-hop alternative route to the destination
  kept in the topology table, ready to be installed
  if the successor fails feasible successors are
  only in the topology table
• Active State
• During route recomputation, routes lost due to a
  successors failure are said to be in the active
  state. The active state ends when the route is
  restored or removed.
• Passive State
• Installed routes that are not in the process of
  being recomputed are said to be in the passive
  state.

6
EIGRP Packet Types

• Hello Packets
• Unreliable multicast to 224.0.0.10 to discover
  and maintain neighbors contains the routers
  neighbor table
• Default hello interval depends on the bandwidth
• 1.544 Mbps 60 sec. hello interval (180
  holdtime)
• gt 1.544 Mbps 5 sec. hello interval (15
  holdtime)
• Update Packets
• Sent reliably, there are 2 types
• Unicast to new neighbor discover contains
  routing table
• Multicast to all neighbors when topology changes
• Query Reply Packets
• Queries are multicast reliably during route
  recomputation, querying neighbors for a new
  successor to a lost route
• Neighbors unicast a reply to the query whether or
  not they have a route.
• Acknowledgement Packets
• Dataless packet that acknowledges the receipt
  of a packet sent reliably

7
Reliable Transport Protocol

• RTP is EIGRPs flexible protocol used to
  transport message types through a network
• Since EIGRP is protocol independent, it has to
  have its own connection-oriented and
  connectionless services
• RTP allows unicasting and multicasting reliable
  and unreliable packets to peers simultaneously
• RTP maintains a transmission list in the neighbor
  table with sequence numbers to determine when a
  required acknowledgement has been received.
• Works much like TCPs Positive Acknowledgement
  with Retransmission

8
The EIGRP Process

• EIGRP operation is completed in five stages
• Building neighbor relationships
• Discovering routes
• Choosing the best routes
• Maintaining routes
• Removing routes
• These stages do not necessarily occur
  sequentially
• Building relationships and discovering routes
  occur together as do choosing and maintaining
  routers

9
EIGRP Configuration
10
Basic Configuration

• Similar to IGRP, EIGRP is started with the
  following commands
• Router(config)router eigrp AS_number
• Router(config-router)network network-number
• For interfaces whose actual bandwidth is
  different than EIGRPs defaults, use the
  following command.
• Router(config-if)bandwidth kilobits

11
Manual Summarization

• On Router B, you would summarize routes
  advertised to A as follows
• !Start the routing process disable automatic
  summarization
• RTB(config)router eigrp 100
• RTB(config-router)network 190.1.1.0
• RTB(config-router)network 190.1.2.0
• RTB(config-router)network 190.1.3.0
• RTB(config-router)no auto-summary
• !Then on the interface, summarize the subnets
  advertised to A
• RTB(config-router)interface e0
• RTB(config-if)ip address 10.2.50.1 255.255.255.0
• RTB(config-if)ip summary-address eigrp 100
  190.1.0.0 255.255.252.0

12
Bandwidth Optimization

• By default, EIGRP will only consume up to 50 of
  a links configured bandwidth.
• If a link in 256Kbps, then EIGRP traffic will use
  up to 128Kbps
• Why would you want to change the default setting?
• May be necessary when network apps require
  certain amounts of bandwidth at all times.
• Sometimes, EIGRP traffic will require a certain
  level of bandwidth availability.
• Note Changing EIGRPs bandwidth percentage has
  no effect on user traffic.
• Two commands to configure EIGRP traffic
  percentage.
• bandwidth
• ip bandwidth-percent eigrp

13
bandwidth Configuration

• The bandwidth command
• Router(config-if)bandwidth bandwidth
• Configured on the interface where you want to
  adjust EIGRP traffic.
• Whatever value is specified with the bandwidth
  command, EIGRP always takes 50 of it (by
  default).
• Remember The bandwidth command is only used by
  routing protocolsit has no effect on user
  traffic when the protocol is EIGRP. The router
  does not use this command for any other purpose.
• For example, you have a 128kbps link and you only
  want EIGRP to use 16kbps.
• Router(config-if)bandwidth 32
• EIGRP will use, at most, 50 of the configured
  bandwidth
• User traffic will still be allowed to use at
  least 112kbps (128-16)

14
bandwidth-percent Configuration

• The second way to modify how much bandwidth EIGRP
  uses is to use the following command
• Router(config-if)ip bandwidth-percent eigrp
  AS-number percent
• Use this command when you want to specify a
  different percentage than 50 of the configured
  bandwidth.
• For example, you have a 64kbps link and the
  bandwidth has been set to 32kbps for metric
  calculation purposes.
• However, you want EIGRP to be able to use an
  entire 32kbps of the links 64kbps speed, if
  needed.
• Router(config)int s0
• Router(config-if)bandwidth 32
• Router(config-if)ip bandwidth-percent eigrp 123
  100

15
Point-to-Point Configurations

• Hub_Router(config)interface serial 0
• Hub_Router(config-if)encapsulation frame-relay
• Hub_Router(config-if)int serial0.1
  point-to-point
• Hub_Router(config-subif)bandwidth 154
• Hub_Router(config-subif)int serial0.2
  point-to-point
• Hub_Router(config-subif)bandwidth 154
• . . .
• Hub_Router(config-subif)int serial0.10
  point-to-point
• Hub_Router(config-subif)bandwidth 154

16
EIGRP IPX Configurations

• EIGRP and IPX basic routing configurations
• Router(config)ipx routing
• Router(config)ipx router eigrp AS
• To disable IPX RIP updates for a particular
  network
• Since IPX RIP is on by default (no additional
  configurations are needed), to disable updates
  for a specific network...
• Router(config)ipx router rip
• Router(config-ipx-router)no network
  network-number