Cannot figure this EIGRP question out....

Its a flashcard but when I click the answer its all garbled. The question is basically this:

A router in a network segment has been newly installed by a jr admin. The network is running EIGRP AS # 212. The jr. admin. has not correctly configured the router. After correctly entering the AS # 212 the router still does not recieve EIGRP routes as show in the output below (the output is only directly connnected routes, no routed protocols, only "c"'s)

What is causing the router to not recieve EIGRP updates?

It sucks cause this really bothers me. I cannot see the answer. If every thing is configured correctly on all routers what could possible prevent any eigrp updates?

These are my guess's.

1. cdp is not enabled on the router? at a config prompt that would be : enable cdp correct?

2. if the routes are classless EIGRP should be ok with auto-summerization? Im not entirely sure about this.

That is the only 2 things I think could be related but honestly it could be something really easy.

Any ideas would be cool

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Comments

mwgood

Let's see the output.

Probably more there than meets the eye.

zero-g-smith

Its a show ip route command and it lists 3 directly connected routes. But since the question does not list details about other routers I have to assume the ip address are correct and working since the routes have a C in front of them.

keenon

is the interface connecting the routers in eigrp? if they have the same AS that could be the only thing i could see it being.

agustinchernitsky

zero-g-smith wrote:

1. cdp is not enabled on the router? at a config prompt that would be : enable cdp correct?

2. if the routes are classless EIGRP should be ok with auto-summerization? Im not entirely sure about this.

My two cents:

1.- nothing to with this... CDP is a very nice feature to get info from directly connected switches and Routers... not to do with EIGRP. EIGRP uses RTP protocol to send hello and other stuff. I get mixed a lot with CDP VTP STP

2.- Now, this is a posibility... EIGRP does autosummarization by default, as opossed to OSPF, which doesnt. you should issue a "no auto summary" when configuring EIGRP. Also, you should enter the complete classfull address.

Another posibility: Has de Jr Admin configured which networks to advertize? Any passive interfaces?

zero-g-smith

YES EIGRP is being used across . Supposedly the AS numbers match.

I figured the cdp had nothing to do with it but I was just curious.

2.- Now, this is a posibility... EIGRP does autosummarization by default, as opossed to OSPF, which doesnt. you should issue a "no auto summary" when configuring EIGRP. Also, you should enter the complete classfull address.

Ok so if using discontigous networks you have to turn off auto summarize?
Should you use wild card masks then (as this is optional)?

Another posibility: Has de Jr Admin configured which networks to advertize? Any passive interfaces?

The question does not say.

So for furture reference when troubleshooting EIGRP connected routers.

1. make sure all address's correct.
2. make sure AS numbers match.
3. make sure auto summarization is turn off (regardless of ip numbers?)
4. make sure directly connected interfaces are not in passive state.
5. make sure all networks are advertised.

Does that about cover it?

zero-g-smith

actually is this the correct command to take out summarization?

no ip summary-address eigrp as-number network-address subnet-mask [admin-distance] <

optional

the ciscopedia says this about :

no auto-summary

This command applies to a RIP routing process. To restore the default behavior of automatic summarization of subnet routes into network-level routes, use the auto summary router configuration command. To disable this function and transmit subprefix routing information across classful network boundaries, use the no form of this command. RIP Version 1 always uses automatic summarization. If you are using RIP Version 2, you can turn off automatic summarization by specifying no auto-summary. Disable automatic summarization if you must perform routing between disconnected subnets. When automatic summarization is off, subnets are advertised.

so it looks to me like the different protocols use different commands?

agustinchernitsky

no auto-summary turns off auto-summary for EIGRP Allowing you to use discontinued networks.

the command ip summary-address... is used per inteface to summarize the networks that are reachable thru that int.

Wildcards are used with OSPF... or at least I never used them with EIGRP.

I would bet on the auto-summary stuff causing problems!

zero-g-smith

Yes I think your correct. Im gonna have to try to test this in boson net sim.

Thanks for your help

EdTheLad

The problem you have is not down to auto-summarization,if the major network changed between the 2 routers you will still get a summary address advertised in eigrp.If the major net doesnt change you will see the normal unsummarized routes.Either way you will see one or more eigrp learned routes.

I would say there are no routes learned because eigrp was not enabled on the interface between the other router.The question says the Jr admin enabled eigrp with AS 212 and thats all,he must now enable the interface with the network command.

Yankee

I'm with Ed. There is no neighbor relationship established and the best reason for this would be the interface is down or the network command is missing.

Yankee

agustinchernitsky

Yep, its a possibility.

Danman32

They aren't showing the config, so I bet it has to do with the interface IPs.
Lets see that table please.

mzinz

Table screenshot.

No adjacency = no eigrp 212 on the other int.

kelvintan23

mzinz wrote:

Table screenshot.

No adjacency = no eigrp 212 on the other int.

Its the 2nd time i saw this question on my test... and i failed... does any1 know the answer to the questions?

i have put no auto-summary but routes are just not learned

agustinchernitsky

I got the same question... Without breaking the NDA, I have to say that besides fixing the incorrect AS... there was a network not being advertized by one of the routers... so there were no adjacencies created.

Try and remember the Network xxx.xxx.xxx.xxx commands in the routers... you should remember that the network of the interface connecting both routers wasn't advertized.

kelvintan23

try using Net sim to simulate the question during the test, but in vain.
(Try my best to remember the test question :P )

Even if you specify different AS in different router, it seem like the route can still be learned and propagated to other routers.

any1 could provide the actual question or the answers specified in the first post?

agustinchernitsky

Wait... if you specify different AS, no way that can happen...

you know... the no auto-summary if it is discontiguous net should be used too... it won't pass routing tables if the summarization is the same. I did try this in the lab and until I removed the auto-summary, no routes were exchanged... they, they did.

convenientstore

sharing my notes and opinion.

Neighbor Discovery
Before EIGRP routers are willing to exchange routes with each other, they must become neighbors. There are 3 conditions that must be met for neighborship establishment:
a)Hello or ACK received
b)AS numbers match
c)Identical metrics( K values)

I would make sure to
a)ping the interface to make sure you can ping
a1)show ip ospf neighbor to see if it's in fact neighbor
b)make sure network command is there and looks right
c)I would also try to no eigrp and then reenter everything as routing update
do not happen until either new network is entered or for routing update(? how long?)

But that's just my guess. In my lab so far, no auto do not have any affect.

lootitall12345

It wouldn't be because the interface is passive would it? I'm just throwing it out there.