LDP looping protection

[Judy]

Hi,

We have LDP looping in network. Can somebody help me to understand how Juniper implemented LDP looping prevention and detection of MX Routers? What configuration I need?

Thanks,

Judy

[abhilash.rajappan]

Hope the attached PDF helps:

Regards,

Abhilash

[krenjt]

Hi

  What i know is that LDP itself does not have a loop prevention mechanism, it sets up a LSP based on IGP shortest path, so it depends on IGP to provide loop prevention mechanism.

Hope that will help you.

ThankS!

[Judy]

Thanks for your replay!

I have enabled LFA(IP FRR) in our network.  That is why we have two best routes but LDP and IGP have different routes.

I expected IGP route is selected instead of LDP route. 

x.x.x.x./32    *[LDP/9] 00:29:38, metric 681

                    > to x.x.x.101 via ae2.0, Push 700000 ------------->Do not know why LDP pick up ae2. 0

                    [OSPF/10] 18:41:04, metric 681

                    > to x.x.x.121 via ae1.0 --------------------> this one should be selected

                      to x.x.x.101 via ae2.0

Judy

[jackycheung]

LDP got a higher route preference than OSPF!

http://www.juniper.net/techpubs/software/junos/junos94/swconfig-routing/default-route-preference-val...

[Judy]

You are right that LDP has high preference. In our case, LFA is enabled. If LDP and OSPF does not sync correctly, it casues a loop. That is what is happening here. Any clue?

[jasonlai]

Hi,

Have you configure LDP synchronization ?

user@host# show protocols ospf 
area 0.0.0.0 {
            interface so-1/0/3.0 {
                ldp-synchronization {
                      hold-time 10;
                }
            } 
}