LDP Commands

‎06-04-2019 05:59 AM

Hi All,

during my studies about LDP as Signaling Protocol i found the below:



set routing-instances MPLS-VPLS-VLAN20 protocols vpls neighbor
set protocols ldp session authentication-key "abcdef"


The first one should be

"Specify each of the PE routers participating in the VPLS domain. Configuring this statement enables LDP for signaling VPLS."


The second one is for:

"Configure LDP session parameters by specifying the session destination address."


As far as I understood the first one is needed for enabling LDP, so is a must to have command 

The second command is only in case we want to use authentication between the LDP peers.

Could you please someone confirm?

More, analising the network, I have only 2 PE devices and MPLS/LDP is active between them.

Is there any way to distinguish, in the configuration, which signaling protocol is used to establish the transport tunnel(outer label)

and which signaling protcol is instead used for the inner label? (In this case the "service" which use the mpls is vpls).

As far as i understood so far, from my studies, the typical situation is

PE1 <-> P <-> PE1


In this case are needed 2 LDP session between 

PE1 <->P


P <-> PE2

for creating the transport protocol


and LDP session (targeted LDP session i guess) beetwen

PE1 <->PE2 

for exchange the "inner" label.

In my case the topolgy is simple

PE1 <-> PE2 and is confusing me on how can i distinguish the 2 case above mentioned.


Thanks all!!

Accepted by topic author FabNewCert
‎06-13-2019 08:48 AM

Re: LDP Commands

‎06-04-2019 06:51 AM

To enable LDP, here's very basic command:

set protocols ldp interface <>

set protocols ldp interface lo0.x


I think what you want to ask is for LDP signalled VPLS 

#1 command: This will create targeted LDP session (with assumption that underlay ldp neighbors are all established) 

#2 commadn: Your understanding is correct. 


"show vpls connection" is the best way to check vpls related status. To find out whether it is using BGP or LDP as signaling protocol, I would say you need to check from configuration perspective. To check the inner label, you can also use "show route forwarding-table family vpls", you should see "push push(Top)" option 

Mengzhe Hu

Re: LDP Commands

‎06-07-2019 01:21 AM
Hi mhu, Thank you for your time and answer which was very useful. The main problem here was that I mixed up the concept of PW and LSP. After reading tons of documentation i reached this conclution: - LSP are the tunnel for transport - PW are instead tunnel for the service (vpls in my case) which run above the mpls network. Next: to understand which protocol is used for build the LSP is enough to run the command show mpls lsp extensive This allow to see for example messages like "Received RRO", "Computed ERO" and without doubt this indicate the use of RSVP protocol to create the tunnel. Confirmation arrive also form the configuration (set protocols rsvp interface xx) Next: to understand which protocol is used for build the PW is enough to run show ldp session, besides a check at configuration level (e.g. check if lsp are statictally defined as suggested by you above). Next: to check the service lable is enough the command show vpls connections Next: to check the tranpsort label show route table mpls.0 protocol rsvp Next: to check and see the operation involing inner and outer lable is enough the command "show route forwarding-table family vpls". Does it make sense? Thanks!

Re: LDP Commands

‎06-07-2019 06:56 AM
Hi, Thanks for your reply. Most of your understanding is correct. Thanks to tons of reading. Only thing I'd like to high light here, you will not only have rsvp lsp as mpls transport (out label). Another widely used label distribution protocol is ldp. You can use "show ldp neighbor/session/database" to get ldp related information. It assigns label just like RSVP LSPs.

Mengzhe Hu

Re: LDP Commands

‎06-10-2019 01:25 AM
I tried to accept your answer as solution but the website has some problem. I will try again later. Thanks for your time.

Re: LDP Commands

‎06-12-2019 12:30 AM

Few cli commands which may be interesting to you while troubleshooting,


Few Ldp cli commands,


show ldp session

show ldp path

show route <one of vpn route> table <vpn>.inet.0

show ldp database

show route table inet.3

show route <PE/RR loopback> | no-more

show route <PE/RR loopback>  details| no-more

show route forwarding-table destination <PE/RR loopback> | no-more

show ldp neighbor | no-more

show ldp session | no-more

show ldp neighbor details | no-more

show ldp session details | no-more





set protocols ldp traceoptions flag route detail

set protocols ldp traceoptions file ldp-trace size 10m files 10

set protocols ldp traceoptions flag label detail

set protocols ldp traceoptions flag binding detail

set protocols ldp traceoptions flag error detail



show mpls lsp ingress

show configuration potocols mpls

show mpls lsp ingress extensive

show mpls lsp

show rsvp session detail ingress


#Please mark my solution as accepted if it helped, Kudos are appreciated as well.