Routing

Hi all.

I am hoping you can help me with trying to learn how JunOS is configured for LDP targeted peers. I have been going around in circles and just cannot seem to break out of my "other vendor" way of thinking..

I am a newbie to the Junos universe and way of thinking, and trying to broaden my knowledge to the Junos/Juniper side.

I have a Juniper MX-80 router with Junos ver. 12.3R6.6.

Essentially, I am trying to do the equivalent to Cisco's global command for a targeted LDP peer:

cisco(config)#mpls ldp neighbor <ip-address> targeted ldp

I have done a LOT of searching and finally found the following document:

http://www.juniper.net/techpubs/software/erx/junose93/swconfig-bgp-mpls/ldp-discovery-mechanisms.html

Unfortunately, I have not found much else that I have found helpful to me. Maybe I am not searching the correct terms for Junos/Juniper or something along those lines.

When I search on "mpls ldp targeted hello send list" I get the following document which is very vague:

http://www.juniper.net/techpubs/en_US/junose10.3/information-products/topic-collections/command-reference-a-m/mpls-ldp-targeted-hello-receive-list.html

When I try this I get the following:

!

MX-80> edit

Entering configuration mode

[edit]
MX-80# set mpls
                    ^
syntax error.

!

So, my plea is to have a Junos/Juniper Guru help me learn the Junos way of thinking "LDP targeted neighbours" and how Junos/Juniper achieves this as compared to the Cisco way. I am afraid that I have not had much success with what I have read so far in the Junos documentation.

I have LDP and MPLS configured on both devices, as well as OSPF which is in the FULL state and all routes present in the routing tables on both devices, including all the /32 loopback IP's. All interfaces on my network are reachable from anywhere for now.

My final goal is to establish an MPLS LSP between two devices which are not directly connected, one being a Cisco device and the other being a Juniper MX-80 device.

My other goal is to UNDERSTAND why and how Junos/Juniper acheive the LDP targeted mechanism, and how it is different from the Cisco way of doing it.

If there is a helpful Juniper document that I can read, I am happy for any suggestions.

Thanks!

Conlan

Hi,

In Juniper u just need to put the interface that want participate on ldp under protocol ldp.

Thanks Surya!

That looks to be the very thing I am looking for.

I will give it a try and see if that works.

I am optimistic it will do the trick for me.

Hi,

It should be easy, you only need:

1. set protocols ldp interface <interface-name>
2. set interface <interface-name> family mpls

Line 1 will make the specified interface participate in the LDP topology, i.e. she will try to establish neigborships to directly connected peers.

Line 2 is mandatory and will make sure your interface is able to process MPLS packets

Typically your LDP and IGP topology are the same. i.e. probably you would want that all interfaces runngin an IGP also run LDP.

If a path exists all along the network between two remote routers then those routers will be able to know each other hop-by-hop throuh LDP. Thus you should see each other's loopback in inet.3 table. Those remote routers do not need to peer together. They don't require a targeted-LDP session to establish the transport LSP which seem to be your goal.

Typically I remember only two situations where Targeted-LDP is required, meaning two non-directly connected routers will establish a LDP session:

1. L2CKT or LDP-VPLS signalization
2. LDP over RSVP

In both cases you need to add this configuration : set protocols ldp interface lo0.0

In case 1. a T-LDP session will be established for each configured neighbor.

In case 2. a T-LDP session will be established to the remote end of RSVP LSPs configured with ldp-tunneling.

Another point you should be aware of is that big difference between Junos and "another vendor" : by default Junos advertises only its loopback address through LDP (and as said previously that address associated with a LDP label is installed in inet.3 which means by default it will be available only for BGP next-hop resolution)

Finally: the links you have shared are for JunosE not for Junos. (JunosE is an OS running on E-series)

Please refer to this link instead http://www.juniper.net/techpubs/en_US/junos14.1/information-products/pathway-pages/config-guide-mpls-applications/config-guide-mpls-applications-ldp.html

Thank-you pantunes.

I have found your post VERY helpful and insightful. You are quite correct, Juniper/Junos LDP over RSVP is what I was ultimately working on to understand in this case. It is quite different to what I was used to after many years of doing it in a particular way. I have learnt something 🙂

I was just not able to put together that "ldp-tunneling" would be the key to Targeted peers, I was too busy looking under [protocols ldp] or a configuration very similar to what I was used to from the other vendor.

Thanks for the link, I will be investing some more time into it. I was not aware JunosE was different, but looking back on it now with a little additional information it is so obvious 🙂

Hi conlan,

You probably don't need to know how to use ldp-tunneling now as its seems you're doing your first steps with Junos. But for more advanced scenarios you should be aware that this feature allows a RSVP LSP to tunnel a LDP LSP. I just mentioned this as an example where you need targeted-LDP sessions.