EIGRP

1
EIGRP

• Enhanced Interior Gateway Routing Protocol

2
What is EIGRP?

• Enhanced Interior Gateway Routing Protocol
  (EIGRP) is an advanced version of IGRP.
• Provides superior convergence, operating
  efficiency and combines link-state protocol with
  distance-vector protocols.

3
Advantages of EIGRP

• low usage of network resources during normal
  operation
• when a change occurs, only routing table changes
  are propagated, not the entire routing table,
  this reduces the load the routing protocol itself
  places on the network
• rapid convergence times for changes in the
  network topology

4
Neighbor Discovery

• EIGRP uses non-periodic incremental routing
  updates.
• EIGRP only sends routing updates about paths that
  have changed when those paths change.

5
How EIGRP Works?
A typical distance vector protocol saves the
following information when computing the best
path to a destination the distance (total metric
or distance, such as hop count) and the vector
(the next hop). For instance, all the routers in
the network in Figure 1 are running Routing
Information Protocol (RIP). Router Two chooses
the path to Network A by examining the hop count
through each available path.
6
How EIGRP Works?
Since the path through Router Three is three
hops, and the path through Router One is two
hops, Router Two chooses the path through One and
discards the information it learned through
Three. If the path between Router One and Network
A goes down, Router Two loses all connectivity
with this destination until it times out the
route of its routing table (three update periods,
or 90 seconds), and Router Three re-advertises
the route (which occurs every 30 seconds in RIP).
7
How EIGRP Works?
EIGRP, instead of counting on full periodic
updates to re-converge, builds a topology table
from each of its neighbor's advertisements
(rather than discarding the data), and converges
by either looking for a likely loop-free route in
the topology table, or, if it knows of no other
route, by querying its neighbors. Router Two
saves the information it received from both
Routers One and Three
8
How EIGRP Works?
It chooses the path through One as its best path
(the successor) and the path through Three as a
loop-free path (a feasible successor). When the
path through Router One becomes unavailable,
Router Two examines its topology table and,
finding a feasible successor, begins using the
path through Three immediately.
9
Properties of EIGRP

• EIGRP can route IP, IPX and AppleTalk.   Along
  with IS-IS, which is one of the few
  multi-protocol routing protocols
• The Diffusing Update Algorithm (DUAL) is the
  heart of EIGRP.  In essence, DUAL always keeps a
  backup route in mind, in case the primary route
  goes down.  DUAL also limits how many routers are
  affected when a change occurs to the network
• There is no maximum allowable number of hops.  In
  a EIGRP network, each router multi-casts "hello"
  packs to discover its adjacent neighbor. This
  adjacency database is shared with other router to
  build a topology database.  From the topology
  database the best route (Successor) and the
  second best route (Feasible Successor) is found

10
Properties of EIGRP

• EIGRP is classless, meaning it does include the
  subnet mask in routing updates. However, by
  default 'auto-summary' is enable.  You must
  disable if you want subnet information from other
  major networks
• The EIGRP metric is a can be a complex
  calculation, but by default it only uses
  bandwidth and delay to determine the best path.

11
EIGRP v.s Other Routing Protocols
12
Configurations and Show Commands for EIGRP
Routerconf tEnter configuration commands, one
per line. End with CNTL/Z.Router(config)router
EIGRP 200Places you in Router EIGRP Config mode,
the '200' is the Autonomous system (AS) number. 
On routers with the same AS number will share
information.Router(config-router)network
10.0.0.0Enables EIGRP on all interfaces that are
part of the Class A 10.0.0.0Router(config-router)
network 157.89.0.0Router(config-router)network
200.1.1.0Router(config-router)RouterTo
debug   debug ip eigrpTo view routing table 
show ip routeTo view IP address  show ip int
brief To view the EIGRP Topology table show
eigrp topology all-links To view EIGRP key
statistics show eigrp traffic
13
EIGRP Scenario and Router Configurations

• Based on 3 Routers Meshed

14
Dallas Router
Dallas Router Configuration Singaporeshow
running-config Building configuration... Current
configuration ! version 12.0 service timestamps
debug uptime service timestamps log uptime no
service password-encryption ! hostname
Dallas ! ! ! ip subnet-zero no ip
domain-lookup ! ip audit notify log ip audit po
max-events 100 ! ! process-max-time
200 ! interface FastEthernet0/0 ip address
192.168.232.1 255.255.255.0 no ip
directed-broadcast no keepalive !
interface Serial0/0 ip address 192.168.224.2
255.255.255.252 no ip directed-broadcast no ip
mroute-cache no fair-queue clockrate
56000 ! interface BRI0/0 no ip address no ip
directed-broadcast shutdown isdn guard-timer 0
on-expiry accept ! interface Serial0/1 ip address
192.168.240.1 255.255.255.252 no ip
directed-broadcast clockrate 56000 ! router eigrp
100 network 192.168.224.0 network
192.168.232.0 ! router igrp 100 network
192.168.240.0 ! ip classless no ip http
server ! ! line con 0 logging synchronous transpor
t input none line aux 0 line vty 0 4 ! ! no
scheduler allocate end
15
Orlando Router
Orlando Router Configuration SanJose3show
running-config Building configuration... Current
configuration ! version 12.0 service timestamps
debug uptime service timestamps log uptime no
service password-encryption ! hostname
Orlando ! ! ! ! ! ! ip subnet-zero no ip
domain-lookup ! ip audit notify log ip audit po
max-events 100 ! ! ! process-max-time
200 ! interface Serial0/0 ip address
192.168.224.1 255.255.255.252 no ip
directed-broadcast no ip mroute-cache no
fair-queue ! interface Serial0/1 ip address
192.168.228.1 255.255.255.252 no ip
directed-broadcast no ip mroute-cache no
fair-queue ! interface BRI0/0 no ip address no ip
directed-broadcast shutdown isdn guard-timer 0
on-expiry accept
! interface FastEthernet0/0 ip address
192.168.1.3 255.255.255.0 no ip
directed-broadcast no keepalive ! interface
Serial0/1 no ip address no ip directed-broadcast s
hutdown ! router eigrp 100 network
192.168.0.0 network 192.168.1.0 network
192.168.224.0 ! ip classless no ip http
server ! ! line con 0 logging synchronous transpor
t input none line aux 0 line vty 0 4 ! ! no
scheduler allocate end
16
New York Router
New York Router Configuration NewYorkshow
running-config Building configuration... Current
configuration ! version 12.0 service timestamps
debug uptime service timestamps log uptime no
service password-encryption ! hostname
NewYork ! ! ! ! ! ! ip subnet-zero no ip
domain-lookup ! ip audit notify log ip audit po
max-events 100 ! ! ! process-max-time
200 ! interface FastEthernet0/0 ip address
192.168.248.1 255.255.255.0 no ip
directed-broadcast no keepalive ! interface
Serial0/0 ip address 192.168.240.2
255.255.255.252 no ip directed-broadcast no ip
mroute-cache no fair-queue ! interface
Serial0/1 ip address 192.168.228.2
255.255.255.252 no ip directed-broadcast shutdown
!
! router eigrp 100 network 192.168.240.0 network
192.168.248.0 ! ip classless no ip http
server ! ! line con 0logging synchronous transport
input none line aux 0 line vty 0 4 ! ! no
scheduler allocate end