EIGRP configuration.

[andy_tomlinson]

Hi,

Just a quick configuration question about EIGRP.

Lets say I have 6x 2600 Routers in a ring topology using the Serial interfaces: 2600A -> 2600B, 2600B -> 2600C ...etc... 2600E -> 2600F, 2600F -> 2600A and I want to use the EIGRP routing protocol.

2600A -> 2600B is using network 192.168.0.0

2600B -> 2600C is using network 192.168.1.0

.

.

2600E -> 2600F is using network 192.168.4.0

2600F -> 2600A is using network 192.168.5.0

So presumably, I connect to each router - configure each interface with addresses in the appropriate network, and then configure EIGRP with the same AS number on each router, and then add each network?

Thanks, Andy.

P.S. Sorry - perhaps this should have been posted in WANs rather than LANs! Ooops!

[Georg Pauwen]

Hello Andy,

you are right, you can configure each router with the same EIGRP AS number and then add the interfaces to your configuration. It is also advisable to configure a Loopback interface for each router, the address of which can then be used as the EIGRP router ID. So the configuration per router could look like this:

2600A

!

interface Loopback0

ip address 1.1.1.1 255.255.255.255

!

interface Serial0/0

ip address 192.168.0.1 255.255.255.0

!

router eigrp 1

eigrp router-id 1.1.1.1

network 1.1.1.1 0.0.0.0

network 192.168.0.1 0.0.0.0

no auto-summary

The remaining routers can be configured in a similar fashion. Keep in mind that the ´network´ statement does not actually advertise a network, it just specifies which interface is being advertised in EIGRP (that is why the mask 0.0.0.0 in the network statement is being used in my example).

Does that make sense ?

Regards,

GP

[Richard Burts]

Georg makes good points and is pointing you in the right directions. There is one peice that he did not include which is that you need to configure the connections from 2600F to 2600A and include it in EIGRP. So the configuration should include:

interface serial 0/1

ip address 192.168.5.2 255.255.255.0

router eigrp 1

network 192.168.5.2 0.0.0.0

HTH

Rick

[Kevin Dorrell]

Rick,

To get the most efficient routing, each router needs to for adjacencies with its neighbor on both sides round the loop. Otherwise the traffic would always go in one direction round the loop only, like a road traffic island.

Just FMI, in EIGRP does the router ID have to reachable for the protocol to work, or is it like OSPF where it does not matter? I am guessing the latter because of 224.0.0.10 being a multicast, and because the neighbors are discovered automatically. In that case the network 1.1.1.1 0.0.0.0 would useful for readability, but not essential.

Kevin Dorrell

Luxembourg

[Georg Pauwen]

Hello Kevin,

the router-id in EIGRP indeed does not have to be reachable, as a matter of fact, I think it is used only on external routes to prevent loops. I usually add it anyway for predictability, and make the associated loopback interface reachable for testing and troubleshooting purposes...

Regards,

GP

[andy_tomlinson]

Hi!

Thanks for all your replies so far.

I'm using RouterSim to practice, after using the Learnkey CCNA CBT courses ... so bear with me!

When I first read the replies I was a little confused but now I've had the weekend to think about it they make a little more sense!

I'm aware EIGRP is VLSM aware/capable but for simplicity's sake I was just using classfull addressing.

When you said the 'network' command is actually relating to the interface you want to participate in the routing that confused me - and the fact that you had interface addresses and not network addresses in the configuration ... but I *think* it makes sense now!

I also read something else that indicated that I should only add the routes to the router for the networks to which it was directly connected - instead of all the networks ... which I guess makes sense from an administrative standpoint!

I've just downloaded the EIGRP configuration guide from the Cisco website so I will peruse that this afternoon and try again.

No doubt I will be back with more questions! :)

Thanks from a slightly confused but now even more keen Andy.

[sebastian.wiegand]

Hi Andy,

well u did'nt understood all Kevin and GP pointed out.

With the EIGRP network command u wont set networks that are routed. Unlike in other Routing Protocols. Here u show EIGRP the Interfaces that participate in the routing Process.

eg.

u have the following interfaces configured:

int Fa0/1

ip add 192.168.1.1 255.255.255.192

int fa0/2

ip add 192.168.2.1 255.255.255.192

int fa0/3

ip add 192.168.1.65 255.255.255.192

aso.

So u configured under your EIGRP the following network statements

router eigrp 1

network 192.168.1.0 0.0.2.255 (thats what u probably would configure)

but in this case Routing Updates will be send through every interface which have an ip in this Range. (Fa0/1,0/2,0/3)

Imagine that on Fa0/3 there is a LAN with nodes that dont need to now about routing in your lan.

Then your network statements will probably look like that:

network 192.168.1.1 0.0.0.0

network 192.168.2.1 0.0.0.0

now only on interface fa0/1 and 0/2 routing updates are sent and adjacencies formed.

Regards,

Sebastian