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Beginner

Stop EIGRP sending hello but continue receiving

Hi,

 

I wll be pleased to know if anyone guide me for how to STOP Eigrp, sending HELLO packets but keep on receiving?

I just tried to use commands as follow:

#access-list 1 deny any

#router eigrp 1

#distribute-list 1 out gig0/0 (I'm using gig0/0 as my outside interface to neighbor)

 

But RTR is still sending and receiving HELLO packets.

 

Regards,

MJM

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Cisco Employee

Re: Stop EIGRP sending hello but continue receiving

Hello Muhammad,

All the best in 2019! :)

Regarding your initial question: No, it is not possible to stop EIGRP sending Hellos and yet keep the adjacency up. Think of this: EIGRP is an event-driven protocol, exchanging route updates only if there is a topology change. If the network is stable, there will be no updates whatsoever. However, this would also mean that a router would not be able to tell these two events apart:

  • No updates are received because there are no topological changes in the network (and in this case, nothing needs to be done since everything is working perfectly)
  • No updates are received because the neighbor has died (and in this case, we need to forget all routes learned from this neighbor and recalculate the routing table)

Therefore, we absolutely rely on sending and receiving periodic Hello packets since they, among other purposes, allow the routers to know that they are still alive and running. We cannot stop the Hellos and expect EIGRP to still continue working as if nothing happened.

You are perhaps referencing the old trick using passive interfaces in RIP - a passive interface in RIP stopped sending out updates but still continued to process received updates. However, RIP was a timer-driven protocol, sending updates every 30 seconds even if there was no topology change, that's why this trick was possible. That being said, the behavior of passive interfaces in RIP was in fact quite cumbersome, and does not apply to any other routing protocol.

Feel welcome to ask further!

Best regards,
Peter

9 REPLIES 9
Enthusiast

Re: Stop EIGRP sending hello but continue receiving

The interface which dont want to be send or received the eigrp hello packets should make as passive interface example is as below

 

config t 

router eigrp 1

passive-interface Gi0/0

end

 

Kindly rate for helpful post

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Beginner

Re: Stop EIGRP sending hello but continue receiving

Hi,

 

I want my EIGRP running router to only send HELLO packets but not want to receive hello packets at the same Time/Device.

With that my neighborship should remain established.

Please advice if any have the idea about?

 

Regards,

Anon

Everyone's tags (1)
Beginner

Re: Stop EIGRP sending hello but continue receiving

Hi!

 

I don't know why you would want that but you could use an ACL on the interface denying packets from or for 224.0.0.10, you can also use the eigrp neighbor command too but that would disable dynamic discovery for EIGRP if I'm not wrong.

The distribute list command will only prevent the EIGRP process to send any subnets

 

ACL would prevent neighborship from forming and would be like this

 

ip access-list extended NOEIGRP

 deny ip any 224.0.0.10

 permit ip any any

 

interface gig 0/0

 ip access-group NOEIGRP out                         -        this one would be to prevent outgoing hello packets 

 

 ip access-group NOEIGRP in                           -        this one would be to prevent incoming hello packets 

 

Someone please correct me if I'm wrong.

The neighbor command needs to be applied in both peers to form a neighborship

 

router eigrp 1

 neighbor 192.168.0.2 gig 0/0

Beginner

Re: Stop EIGRP sending hello but continue receiving

Hello,

If your router doesn't receive hello packets from its peer, hold time will expire and your neighborship will be terminated. Because EIGRP Hold Timer works a little bit different. If your routers have 5 Sec Hello, 15 Sec Hold Time configured, this means that Your router sends Hello packets every 5 Sec and If your neighbor doesn't receive hello packets from your router in 15 Sec, your peer terminates neighborship.

Thank you.
Beginner

Re: Stop EIGRP sending hello but continue receiving

 

Thanks for you Answer I can understand now what I did't focus on. Can you please tell me that is there any possibility to configure Eigrp device with condition as I've defines but peer remains UP(without  neighborship termination).

 

Anon

Hall of Fame Cisco Employee

Re: Stop EIGRP sending hello but continue receiving

Hello Muhammad,

All the best in 2019! :)

Regarding your initial question: No, it is not possible to stop EIGRP sending Hellos and yet keep the adjacency up. Think of this: EIGRP is an event-driven protocol, exchanging route updates only if there is a topology change. If the network is stable, there will be no updates whatsoever. However, this would also mean that a router would not be able to tell these two events apart:

  • No updates are received because there are no topological changes in the network (and in this case, nothing needs to be done since everything is working perfectly)
  • No updates are received because the neighbor has died (and in this case, we need to forget all routes learned from this neighbor and recalculate the routing table)

Therefore, we absolutely rely on sending and receiving periodic Hello packets since they, among other purposes, allow the routers to know that they are still alive and running. We cannot stop the Hellos and expect EIGRP to still continue working as if nothing happened.

You are perhaps referencing the old trick using passive interfaces in RIP - a passive interface in RIP stopped sending out updates but still continued to process received updates. However, RIP was a timer-driven protocol, sending updates every 30 seconds even if there was no topology change, that's why this trick was possible. That being said, the behavior of passive interfaces in RIP was in fact quite cumbersome, and does not apply to any other routing protocol.

Feel welcome to ask further!

Best regards,
Peter

Hall of Fame Master

Re: Stop EIGRP sending hello but continue receiving

Peter has given an excellent explanation. I would add a comment to supplement it. Several of the suggestions involve using an access list to stop the advertisements. It is possible (but as Peter has explained it is not desirable) to use an access list to suppress receiving EIGRP hello packets. It is not possible to use an access list to suppress sending hello packets. The issue here is that an outbound acl will not filter packets generated by the router itself.

 

HTH

 

Rick

Beginner

Re: Stop EIGRP sending hello but continue receiving

@Peter Paluch @Richard Burts Thank you for your corporation. Hopeful to get suitable solutions in case I found issues.

VIP Expert

Re: Stop EIGRP sending hello but continue receiving

As Peter and Rick have explained, your requirement doesn't appear possiible with EiGRP. However OSPF's demain circuit feature suppresses it's usage of hellos after the two neighbors have established synchronization. If you must continue to use EIGRP, you might admend the hello interval to make it occur much less often then it does by default.
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