IPv4 EIGRP 4.1

hi all

I am getting

R1#

*Jul 15 22:20:02.839: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor 10.1.121.21 (Ethernet0/0.121) is up: new adjacency

R1#

*Jul 15 22:21:22.421: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor 10.1.121.21 (Ethernet0/0.121) is down: retry limit exceeded

and


R2#

*Jul 15 22:24:13.730: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor 10.1.221.21 (Ethernet0/0.221) is up: new adjacency

R2#

*Jul 15 22:25:33.331: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor 10.1.221.21 (Ethernet0/0.221) is down: retry limit exceeded




where SW1 is not forming neighborships

does anyone have a solution

Comments

  • Hi ajg,

    Did you get the answer for this problem?

  • In EIGRP, all it takes is receipt of an EIGRP Hello packet from a connected-router to display that, "up: new adjacency" message. However, unfortunately, this message is displayed a bit too prematurely because after receipt of that Hello packet, your local router will send an EIGRP Update Packet (with the "Init" bit set) and will need to get an acknowledgement for that packet. It is only after your Update has been Acknowledged that you truly have a functional neighbor (receiving his Hello packet is only half the battle).

    Several things could happen which might prevent you from getting that Acknowledgement to your initial Update (such as an ACL preventing YOUR packets from reaching the router from whom you just received a Hello. Or possibly extreme network congestion in the path from you to that connected router). So in reality, an EIGRP neighborship is not really usable until both routers have exchanged initial Update packets and both have received Acknowledgements. If you don't receive an Acknowledgement to your initial Update packet within a reasonable time, EIGRP displays the message, "down: retry limit exceeded"

    I would start troubleshooting by trying to verify if (in your case) the 10.1.221.21 router is actually really receiving your EIGRP Hello and Update packets. To start with, can you ping 10.1.221.21? Is there an ACL on that router denying reception of EIGRP packets? Does the output of "show interface" on that router display a lot of dropped packets?

    That's the approach I'd suggest looking into.

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