EIGRP (Enhanced Interior Gateway Routing Protocol)
EIGRP
is a Cisco proprietary advanced distance vector routing protocol, that works on
layer 3 of the OSI model. It uses UDP protocol with port no 88. it is a
classless routing protocol that Supports VLSM/CIDR and auto summarization.
EIGRP
uses autonomous system numbers for making a neighbor relationship. It uses AS
no. starting from 1 to 65535. Since EIGRP is an Interior Gateway Routing
protocol hence it works within the same autonomous system number, which means two
EIGRP speak routers can become neighbor if they connect with the same AS no., different
AS no. can’t connect, and if you want to make neighbor ship between two
different AS then you will have to configure redistribution between two
different AS.
EIGRP
Administrative distance uses 5 for the summary route, 90 for internal, and 170
for external EIGRP (Redistributed Route). Metric uses bandwidth and delay of
line.
EIGRP
supports a maximum of 255 hops and a default of 100 hops. it uses a DUAL
algorithm for finding the best path. It supports equal and unequal cost load
balancing. Load balance up to 4 equal cost paths and max up to 6.
EIGRP
Timers: It uses triggered updates. Hello, the time is 5 sec, and the dead
interval is 15 sec. It uses RTP to maintain communication between Eigrp neighbors,
it uses multicast address 224.0.0.10 for communication. Eigrp uses PDM (Protocols
Dependent Modules) that support multiple protocols such as IPv4, IPV6, IPX, AppleTalk.
EIGRP
Messages Type –
·
Hello-
It is used to discover EIGRP neighbors by using multicast address 224.0.0.10.
·
Update-It
is used to update converged routes to other EIGRP speak routers.
·
Query-
If any successor route fails then EIGRP sends a Query message.
·
Reply-
If the EIGRP speak router receives any Query message then it will Reply.
·
Acknowledgment-
This is used to confirm that the EIGRP packet is delivered reliably.
EIGRP
Tables – EIGRP
uses three tables
·
Neighbor
table- It contains directly connected neighbors'
details.
·
Topology
table- the topology table contains all possible routes.
·
Routing
table- the routing table contains the best route.
EIGRP
Authentication- EIGRP
does not support plain text authentication, it supports only MD5 (Message
Digest 5) authentications.
The
following conditions must match for making EIGRP neighbour relationship-
·
AS no. must match
·
Hello and Dead interval
must match
·
If authentication then
authentication must match.
·
The metric ‘K’ value must
match.
EIGRP uses
5 metric calculations for redistribution- 1. Bandwidth, 2. Delay, 3. Load, 4.
Reliability, 5. MTU,
EIGRP Feasible
Distance- Distance
from source to destination.
EIGRP Advertised
Distance or Reported Distance- Distance
from neighbor to destination.
EIGRP Successor
Route- The
best route with the lowest cost, that is installed in the Routing Table.
EIGRP Feasible
successor Route– Second
best route, if the successor route fails then the feasible successor route takes
over and is installed in the Routing Table.
EIGRP
Feasible Condition- A route will not be installed in the routing table if the advertised
distance is more than the feasible distance.
EIGRP Passive-Interface-
EIGRP uses a passive interface that stops all incoming and outgoing updates from neighbors. You can enable a passive
interface on any interface or you can use the default keyword to block all
interfaces.
How to Configure EIGRP Equal Cost Load Balancing
R1 Configuration
Router(config)#do sh ip protocol
Router(config)#router
eigrp 10
Router(config-router)#net
1.0.0.0
Router(config-router)#net
3.0.0.0
Router(config-router)#net
10.0.0.0
Router(config-router)#no
auto-summary
Router(config-router)#do
wr
Verification-
Router(config-router)#do
sh ip route
Router(config-router)#do
sh ip protocol
Router(config-router)#do
sh ip eigrp topology
Router(config-router)#do
sh ip eigrp neighbor
R2 Configuration
Router(config)#do sh ip protocol
Router(config)#router
eigrp 10
Router(config-router)#net
1.0.0.0
Router(config-router)#net
2.0.0.0
Router(config-router)#no
auto-summary
Router(config-router)#do
wr
Verification-
Router(config-router)#do
sh ip route
Router(config-router)#do
sh ip protocol
Router(config-router)#do
sh ip eigrp topology
Router(config-router)#do
sh ip eigrp neighbor
R3 Configuration
Router(config)#do sh ip protocol
Router(config)#router
eigrp 10
Router(config-router)#net
2.0.0.0
Router(config-router)#net
4.0.0.0
Router(config-router)#net
20.0.0.0
Router(config-router)#no
auto-summary
Router(config-router)#do
wr
Verification-
Router(config-router)#do
sh ip route
Router(config-router)#do
sh ip protocol
Router(config-router)#do
sh ip eigrp topology
Router(config-router)#do
sh ip eigrp neighbor
R4 Configuration
Router(config)#do sh ip protocol
Router(config)#router
eigrp 10
Router(config-router)#net
4.0.0.0
Router(config-router)#net
3.0.0.0
Router(config-router)#no
auto-summary
Router(config-router)#do
wr
Verification-
Router(config-router)#do
sh ip route
Router(config-router)#do
sh ip protocol
Router(config-router)#do
sh ip eigrp topology
Router(config-router)#do
sh ip eigrp neighbor
Test
Load Balancing
C:\>tracert
20.0.0.2
C:\>tracert
10.0.0.2
EIGRP
authentication- is used to
secure your router from becoming a neighbor and sending routing updates to unknown
routers. EIGRP uses MD5 (Message Digest 5) authentication.
Steps to configure EIGRP authentication-
1.
Create
Keychain
2.
Assign
Key string
3.
Implement
EIGRP MD5 authentication with EIGRP
EIGRP uses the concept
of key chains. Each key chain can have many keys, just like in real life. You
can specify a different lifetime interval of each key. That way the second key
in a key chain can be used after the first one is expired, the third one after
the second and so on. After you have created a key chain with the corresponding
keys, you need to enable EIGRP authentication for a particular interface.
The command syntax for
configuration-
#Configure EIGRP
# key chain NAME –
creates a keychain
# key NUMBER – identifies the key number
# key-string STRING – specifies Password
Now enable EIGRP
authentication on an interface.
# ip
authentication mode eigrp AS no. md5 – enables EIGRP authentication on
the interface
# ip authentication key-chain eigrp AS no. Key Chain Name –
specifies the name of the key chain that will be used for authentication
Router Configuration for EIGRP
Authentication-
R1(config)#key
chain chain1
R1(config-keychain)#key
1
R1(config-keychain-key)#key-string
cisco
R1(config-keychain-key)#do
wr
R1(config-keychain-key)#exit
R1(config-keychain)#int
se 0/0
R1(config-if)#ip
authentication key-chain eigrp 10 chain1
R1(config-if)#ip
authentication mode eigrp 10 md5
R2(config)#key
chain chain2
R2(config-keychain)#key
1
R2(config-keychain-key)#key-string
cisco
R2(config-keychain-key)#do
wr
R2(config-keychain-key)#exit
R2(config-keychain)#int
se 0/0
R2(config-if)#ip
authentication key-chain eigrp 10 chain1
R2(config-if)#ip authentication mode eigrp 10 md5
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