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Wednesday, March 12, 2014

How do we configure EIGRP?

What are the steps involved in configuring EIGRP in name mode?

In traditional way we were configuring EIGRP like this:
We go to configuration mode and defining EIGRP with process number
R1#conf t
R1(config)#router eigrp 1
After that if we have to run EIGRP on the interfaces then we have to specify each network with wildcard mask for every interface:
And for some the command like EIGRP authentication, defining Bandwidth to control EIGRP packets or to define EIGRP next-hop you have exit Router config mode and switch to interface mode as shown below:
R1(config)#int fa0/0
R1(config-if)#ip authentication mode eigrp 1 md5
R1(config-if)#ip authentication key-chain eigrp 1 cisco
R1(config-if)#ip bandwidth-percent eigrp 1 75
This was what we discussed for IPv4 Eigrp. Now to run EIGRP for IPv6 we have to configure in different way define the IPv6 router process and run Eigrp under interface mode.
ipv6 router eigrp 1
eigrp router-id
no shut
Interface f0/0
ipv6 enabe
ipv6 eigrp 1

So In traditional way for every address family (IPv4/VRF/IPv6) you have to configure EIGRP separately .You have to switch config mode to interface mode, also another interesting point is that there was no way to configure VRF in traditional IPv6 EIGRP implementation but in “EIGRP Name Mode configuration” you can config all in one place, plus you have the option to run IPv6 Eigrp for VRF
Let’s discussed EIGRP name mode configuration in detail.
EIGRP named configuration is available in following IOS release and onwards:
Cisco IOS XE Release 2.5
If you are running any of the above IOS versions then you will see 2 options after you do question mark as shown. 
R2(config)#router eigrp ?
  <1-65535> Autonomous System
  WORD       EIGRP Virtual-Instance Name
To define Name mode configuration define word option as show below:
R2(config)#router eigrp CISCO

Unlike traditional way, EIGRP instance not create or it doesn't start running the moment following is configured on the router. The instance will be created when address-family and autonomous system number is configured for e.g.:
For IPv4:

R2(config-router)#address-family ipv4 unicast autonomous-system 1
For IPv4 VRF:
R2(config-router)#address-family ipv4 unicast vrf Customer_A autonomous-system 1
For IPv6:
R2(config-router)#address-family ipv6 unicast autonomous-system 1
For IPv6 VRF
R2(config-router)#address-family ipv6 unicast vrf site_A autonomous-system 1
With this Named mode, we can create a single Instance of EIGRP, which can be used for all address family type as shown above.
Another simplicity is if want to turn off the entire AS, you can use “shutdown” command under address-family to turn off the entire instance.
Named EIGRP has 3 configuration modes. These are:
    1) address-family configuration mode - (config-router-af)#
    2) address-family interface configuration mode - (config-router-af-interface)#
    3) address-family topology configuration mode - (config-router-af-topology)#
A) Address-family configuration mode:
In this mode, you can configure networks, EIGRP neighbor, EIGRP Router-id, metric etc. From this mode you can access the other two configuration modes used in EIGRP named configuration.

R2(config-router)#address-family ipv4 unicast autonomous-system 1
Address Family configuration commands:
  af-interface         Enter Address Family interface configuration
  default              Set a command to its defaults
  eigrp                EIGRP Address Family specific commands
  exit-address-family  Exit Address Family configuration mode
  help                 Description of the interactive help system
  maximum-prefix       Maximum number of prefixes acceptable in aggregate
  metric               Modify metrics and parameters for address advertisement
  neighbor             Specify an IPv4 neighbor router
  network              Enable routing on an IP network
  no                   Negate a command or set its defaults
  shutdown             Shutdown address family
  timers               Adjust peering based timers
  topology             Topology configuration mode
B) Address-family interface configuration mode:

This mode takes all the interface specific commands that were previously configured on an actual interface (logical or physical) and moves them into the EIGRP configuration. EIGRP authentication, Bandwidth-percentage, split-horizon, and summary-address configuration are some of the options that are now configured here instead of in interface configuration mode.
R2(config-router-af)#af-interface fa0/0
Address Family Interfaces configuration commands:
  authentication      authentication subcommands
  bandwidth-percent   Set percentage of bandwidth percentage limit
  bfd                 Enable Bidirectional Forwarding Detection
  dampening-change    Percent interface metric must change to cause update
  dampening-interval  Time in seconds to check interface metrics
  default             Set a command to its defaults
  exit-af-interface   Exit from Address Family Interface configuration mode
  hello-interval      Configures hello interval
  hold-time           Configures hold time
  next-hop-self       Configures EIGRP next-hop-self
  no                  Negate a command or set its defaults
  passive-interface   Suppress address updates on an interface
  shutdown            Disable Address-Family on interface
  split-horizon       Perform split horizon
  summary-address     Perform address summarization
In traditional way if we want run EIGRP on all interface we use "network" command. Here you can use“af-interface default” to function same.
R2(config-router-af)#af-interface default

C) Address-family topology configuration mode:
This mode provide several options which operates on EIGRP topology table .here you can define content like redistribution, distance, offset list, variance etc. To enter this mode, we need to go back to address-family configuration mode:
R2(config-router-af)#topology base
Address Family Topology configuration commands:
  auto-summary         Enable automatic network number summarization
  default              Set a command to its defaults
  default-information  Control distribution of default information
  default-metric       Set metric of redistributed routes
  distance             Define an administrative distance
  distribute-list      Filter entries in eigrp updates
  eigrp                EIGRP specific commands
  exit-af-topology     Exit from Address Family Topology configuration mode
  fast-reroute         Configure Fast-Reroute
  maximum-paths        Forward packets over multiple paths
  metric               Modify metrics and parameters for advertisement
  no                   Negate a command or set its defaults
  offset-list          Add or subtract offset from EIGRP metrics
  redistribute         Redistribute IPv4 routes from another routing protocol
  snmp                 Modify snmp parameters
  summary-metric       Specify summary to apply metric/filtering
  timers               Adjust topology specific timers
  traffic-share        How to compute traffic share over alternate paths
  variance             Control load balancing variance
Comparison chart between Eigrp “traditional Configuration” and “Name mode Configuration”:
EIGRP Tradition way of Configuration

EIGRP Name Mode Configuration

int fa0/0
ip add
ip authentication mode eigrp 1 md5
ip authentication key-chain eigrp 1 cisco
ip bandwidth-percent eigrp 1 75 
ip hello eigrp 1 10
IPv6 enable
IPv6 eigrp 1
router eigrp 1
redistribute connected
ipv6 router eigrp 1
eigrp router-id
no shut
router eigrp 2
address-family ipv4 vrf CUST_A
"No IPv6 EIGRP support for VRF"
int fa0/0
ip add
IPv6 enable
router eigrp CISCO
address-family ipv6 unicast autonomous-system 1
  topology base
  eigrp router-id
address-family ipv4 unicast autonomous-system 1
  af-interface FastEthernet0/0
   authentication mode md5
   authentication key-chain cisco
   bandwidth-percent 75
   hello-interval 10
  topology base
   redistribute connected
address-family ipv6 unicast vrf CUST_B autonomous-system 2
  topology base
address-family ipv4 unicast vrf CUST_A autonomous-system 2
af-interface default
  topology base

Citation - This blog post does not reflect original content from the author. Rather it summarizes content that are relevant to the topic from different sources in the web. The sources might include any online discussion boards, forums, websites and others.

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