Download EIGRP

EIGRP
Enhanced Interior Gateway Routing
Protocol
What is EIGRP?
• Enhanced Interior Gateway Routing
Protocol (EIGRP) is an advanced
version of IGRP.
• Provides superior convergence,
operating efficiency and combines linkstate protocol with distance-vector
protocols.
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
Neighbor Discovery
• EIGRP uses non-periodic incremental
routing updates.
• EIGRP only sends routing updates
about paths that have changed when
those paths change.
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.
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).
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
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.
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
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.
EIGRP v.s Other Routing
Protocols
Feature
classful or
classless
metric
periodic
advertisement
advertising
address
administrative
distance
category
RIP v1
RIP v2
OSPF
IGRP
EIGRP
classful
classless
classless
classful
classless
hop count
hop count
composite
(BDRLM)
composite
(BDRLM)
30 seconds
30 seconds
cost
(100,000/b
w)
none
90 seconds
30
seconds
255.255.255.
255
(broadcast)
224.0.0.9
(multi-cast)
255.255.255.
255
(broadcast)
120
120
224.0.0.5
224.0.0.6
(multicast)
110
distance
vector
distance
vector
link-state
distancevector
224.0.0.1
0
(multicast)
Internal
90
External
hybrid
170
100
Configurations and Show
Commands for EIGRP
Router#conf t
Enter configuration commands, one per line. End
with CNTL/Z.
Router(config)#router EIGRP 200
Places 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 10.0.0.0
Enables EIGRP on all interfaces that are part of the Class A 10.0.0.0
Router(config-router)#network 157.89.0.0
Router(config-router)#network 200.1.1.0
Router(config-router)#
Router#
To debug: debug ip eigrp
To view routing table: show ip route
To 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
EIGRP Scenario and Router
Configurations
Based on 3 Routers Meshed
Dallas Router Configuration:
Singapore#show runningconfig
Building
configuration...
Current configuration:
!
version 12.0
service timestamps debug
uptime
service timestamps log
uptime
no service passwordencryption
!
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
Dallas Router
interface Serial0/0
ip address 192.168.224.2 255.255.255.2
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 192.168.240.1 255.255.255.2
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
transport input none
line aux 0
line vty 0 4
!
!
no scheduler allocate
end
Orlando Router Configuration:
SanJose3#show 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
Orlando Router
!
interface FastEthernet0/0
ip address 192.168.1.3 255.255.2
no ip directed-broadcast
no keepalive
!
interface Serial0/1
no ip address
no ip directed-broadcast
shutdown
!
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
transport input none
line aux 0
line vty 0 4
!
!
no scheduler allocate
end
New York Router Configuration:
NewYork#show running-config
Building configuration...
Current configuration:
!
version 12.0
service timestamps debug
uptime
service timestamps log
uptime
no service passwordencryption
!
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
New York
Router
!
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