LDP Neighbor Down detection for backup xconnect

[schwarzenbachcyb]

Hi all

I have the following topology:

On R3 I have a xconnect to R1 with a backup xconnect to R2. Something like this:

interface gigabitethernet 0/1
 xconnect 10.1.1.1 1000 encapsulation mpls
  backup peer 10.2.2.2 1000

R3 sees both neighbours, R1 & R2, over the same uplink interface.

Now R1 crashes and goes offline. What is the right/best mechanism, that R3 can detect this topology change in a fast way? There is no "port down" on R3, it must be some kind of timeout, that R3 switch over to the backup peer over R2.

Should I use BFD with OSPF? Is this enough, that R3 will switch to the backup peer? BFD with LDP neighbours don't exist, if I'm right. Or can I tune some LDP timers?

I also found BFDoVCCV, but this is not supported, when there is a backup peer configured.

I like to have something, that detects the issue in 3 seconds or less.

[Renan Abreu]

I guess you could use BFD on that PW.

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_l2_vpns/configuration/15-s/mp-l2-vpns-15-s-book/wan-l2vpn-pw-red.html#GUID-813C756B-D1EA-435E-8596-B8FC06D5F894

[schwarzenbachcyb]

I don't think that is possible, from the same page:

"Bidirectional Forwarding Detection over Virtual Circuit Connection Verification (BFDoVCCV) with status signaling is supported only on static pseudowires that do not have a backup peer. Explicit configuration of backup peers that violates this restriction is rejected."

I have adjusted the LDP timers to 2/6 and used BFD with OSPF in my lab setup. Currently I have a failover time from around 6 seconds.

I will make some more tests, also with the new ISR1100 series, in the next weeks. Maybe It's different in the current IOS XE Releases or there is something else that I can do.

[Renan Abreu]

Are those devices directly connected? Having BFD for OSPF will not necessarily make it switchover to the backup peer (As the targeted LDP is a TCP session between the peers, so it would try to take any new route to that destination and maintain the session up). I am thinking you can make LDP session shorter maybe? mpls ldp holdtime XXX