Duplicate addresses in MPLS

[nasrul5551]

We have a ASR9010 router in the network, we found out that below error in the logs. after execute the "sh mpls ldp neighbor" command we couldn't find any duplicate addresses. Hopefully will get enlighten as we afraid we overlook at some point. Thank you.

mpls_ldp[1048]: %ROUTING-LDP-4-PEER_DUP_ADDRS : VRF 'default' (0x60000000), 1 Duplicate address(es) advertised by more than one peer

[Peter Paluch]

Hello,

I believe we should trust the message - if the router complains about two or more LDP neighbors claiming the same IP address then most probably, this is indeed the case. Is there any additional logging message accompanying this one that could help narrow down the neighbors claiming the same IP?

If not, using the show mpls ldp neighbor command, verify that you can see all the neighbors that should be peering with your router in LDP, and make note of each one of them. Also make note of any routers missing from this list that should have been present there (either directly connected neighbors or remote neighbors that should have targeted LDP sessions established to this router).

Using this list of neighbors - the ones that show up in the list, and the ones that are missing but should have been there, check each one of them for any IP address conflicts - verify all interfaces configured with IPv4 and IPv6 addresses.

Best regards,
Peter

[JhimRCN]

The first time an %ROUTING-LDP-4-PEER_DUP_ADDRS alarm appears, it is accompanied by the specific IP address which is being claimed by multiple peers. Every following update alarm only shows that a duplictae exists.

Is there a more direct way of accessing the duplicate IP information?

Or any way to re-trigger the initial alarm which contains the duplicate IP address?

[tuananhpro9x]

The first time an %ROUTING-LDP-4-PEER_DUP_ADDRS alarm appears, it is accompanied by the specific IP address which is being claimed by multiple peers.

[mastedarq]

Use below command:

show mpls ldp structs dup-addr

Enjoy.

[nhia_thao@voyant.com]

Hi All, 

We have the same issue and noticed that the HSRP VIP was the duplicated address. The interface inbound ACL was blocking multicast address 224.0.0.2 & 224.0.0.102.

1 permit ip any host 224.0.0.2 (5 matches)
2 permit ip any  host 224.0.0.102

The show mpls ldp structs dup-addr was helpful. It helps you identifying the LDP neighbor where the duplicating IP is coming from. 

[fracjackmac]

Thanks @mastedarq!!

[edhert]

Thanks @mastedarq