Router Ethernet Port Connectivity/Link Loss Detection

steveosgood · ‎10-09-2015

I have a (primary) link between 2 routers that is Ethernet from both routers to media converters. The link is setup to failover to a different (secondary) path if the primary is not passing traffic. The failover works fine, but the primary interfaces on the routers never go down when there is a break between the media converters. Therefore, I cannot tell which path my traffic is taking, and more importantly, when I am single-threaded, unless both paths are down and I lose connectivity. The only way I know it is down is to log into one of the routers and try to ping the other interface.

My question to the community is:

Is there any way to make those interfaces go down if they lose the link to the other side? This is my first post, so please be gentle if this is a stupid question.

Thank You in advance!

-Steve

Zach S · ‎10-11-2015

Steve,

What you want can be accomplished with IP SLA's and tracks. You would tie your normal static route to an SLA that monitors whether or not the router can ping an IP. So in your case it would be pinging the other side of your fiber. You would then tie that SLA to a track, and monitor reachability. Then if your track went down, i.e. if it lost connection to the other side, it would drop the default route tied to the track and use a backup route.

This link will give you a basic overview of setting up an IPSLA and track and how to tie it to a static route.
http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/813-cisco-router-ipsla-basic.html

Follow up question though, are you using any dynamic routing between your routers? Such as OSPF or EIGRP. With dynamic routing the routing process will be aware when a neighbor, or the link attaching the router to the neighbor fails, and perform automatic failover once it's gone too long without a hello packet.

Ganesh Hariharan · ‎10-11-2015

I have a (primary) link between 2 routers that is Ethernet from both routers to media converters. The link is setup to failover to a different (secondary) path if the primary is not passing traffic. The failover works fine, but the primary interfaces on the routers never go down when there is a break between the media converters. Therefore, I cannot tell which path my traffic is taking, and more importantly, when I am single-threaded, unless both paths are down and I lose connectivity. The only way I know it is down is to log into one of the routers and try to ping the other interface.

My question to the community is:

Is there any way to make those interfaces go down if they lose the link to the other side? This is my first post, so please be gentle if this is a stupid question.


Thank You in advance!

-Steve

Hi Steve,

Just for more understanding, Are you saying Two link between two routers acting as Active/Backup and when failover happens the physical interfaces shows always up for primary link on both the end of the router ?

Is my understanding is right ?

-GI

Ganesh Hariharan · ‎10-11-2015

Hi Steve,

Just for more understanding, Are you saying Two link between two  routers acting as Active/Backup and when failover happens the physical interfaces shows always up for primary link on both the end of the router ?

Is my understanding is right ?

-GI

To add to my post as pointed by Zach either you can use IP SLA track or to shutdown the interface you can use IP SLA with EEM scripting as well.

check out the below link for more information ..

https://supportforums.cisco.com/discussion/10794236/shut-interface-if-no-ping-response-using-ip-sla-eem

Hope it Helps..

-GI

Rate if it Helps..