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Use RSVP only for ONE l2circuit

  • 1.  Use RSVP only for ONE l2circuit

    Posted 07-01-2013 05:15

    We're using VPLS and L2VPN on Juniper MX for L2 connections. Signaling is done via BGP and label distribution via LDP.

    Now we want one l2vpn to use a specific path trough the network and not follow the IGP.

     

    I already asked this on the stackexchange site: http://networkengineering.stackexchange.com/questions/449/how-to-force-vpls-l2vpn-to-use-a-specific-path

     

    We came to the conclusion that it would be best to use l2circuit and bind the circuit to a special path with a community, like described here:

     

    http://kb.juniper.net/InfoCenter/index?page=content&id=KB22700&smlogin=true

     

    To do that I enabled RSVP and configured a specific path:
     
    [protocols mpls]
    label-switched-path lsp-l2circuit { to 10.0.0.1; no-cspf; preference 10; primary path-l2circut; } path path-l2circuit { 10.0.0.2 strict; 10.0.0.1 strict; }

     Note the "preference 10". This was done so that the rest (l2vpn, vpls) still follows LDP instead of this path.

     

    Then we set up the l2circuit with a community:

     

    [protocols l2circuit]
    neighbor 10.0.0.1 {
        interface xe-1/3/0.3 {
            virtual-circuit-id 1;
            community l2circuit-community;
        }
    }

     

    And lastly we configured a policy to map this community to the lsp in the forwarding-table:

     

    [policy-options policy-statement l2circuit-mapping]
    term l2circuit-mapping {
        from community l2circuit-community;
        then {
            install-nexthop lsp lsp-l2circuit;
        }
    }
    
    [routing-options forwarding-table]
    export [ ecmp l2circuit-mapping ];

     

    Now this looks good but sadly it doesn't work. 🙂

     

    The l2circuit stays down with error "OL" (no outgoing label).

     

    In the mpls.0 table I see that the RSVP route is there but not active and I assume that that might be the problem:

     

    10.0.0.1/32         *[LDP/9] 1d 20:23:23, metric 1
                               > to 10.0.0.81 via ae4.0, Push 357888
                               [RSVP/10/1] 1d 20:23:08, metric 2001
                               > to 10.0.0.81 via ae4.0, label-switched-path lsp-l2circuit
    

     

    So.. my question is: Is it possible to use RSVP only for a specific l2circuit while using LDP for all other connections? If so, how do I have to configure it to make it work?


    #rsvp
    #MPLS
    #l2circuit
    #ldp


  • 2.  RE: Use RSVP only for ONE l2circuit

    Posted 07-01-2013 05:38

    Hello,

    If RSVP route is inferior to LDP route, then RSVP route won't be used, as You have already discovered.

    You have to use the following:

    1/ secondary IP on tailend/egress LSR' lo0.0

     

    2/ make sure You export this secondary IP into Your IGP

    3/ LDP egress policy on tailend, to insert this secondary IP into LDP

    4/ make sure primary IP stays as tailend' router-id

    5/ on tailend, use BGP export policy to modify BGP nexthop for "everything else" to use secondary IP. Do NOT modify BGP nexthop for Your L2VPN.

    HTH

    Thanks

    Alex



  • 3.  RE: Use RSVP only for ONE l2circuit

    Posted 07-01-2013 05:56

    2/ make sure You export this secondary IP into Your IGP

    3/ LDP egress policy on tailend, to insert this secondary IP into LDP

    4/ make sure primary IP stays as tailend' router-id

    5/ on tailend, use BGP export policy to modify BGP nexthop for "everything else" to use secondary IP. Do NOT modify BGP nexthop for Your L2VPN.



    Hi,

     

    I don't understand step 3 and 5.

     

    3) Why do I have to put the new IP into LDP when I want to use RSVP with it?

     

    5) Why is that? If I build a RSVP path to the new Loopback IP it won't be used for all the other stuff, will it?

     

    All in all I hoped that I could do it without another loopback-ip (We already have two, one for l3vpn/bgp, one for vpls/l2vpn). But if that is what it takes so be it...

     

    I thought that, when I change the next-hop in the forwarding-table, this would override the preference of the route and still use it but that isn't the case it seems.



  • 4.  RE: Use RSVP only for ONE l2circuit

    Posted 07-01-2013 06:10

    Hello,

    My answers :

     



    3) Why do I have to put the new IP into LDP when I want to use RSVP with it?

     

     


    Secondary IP is not inserted into TED by default. You can estalish a RSVP LSP to secondary IP only if You disable CSPF.

    Or You can use "no-install-to" and "install <secondary IP/netmask>" knobs under LSP stanza, to force installation of secondary IP into inet.3

    But then You have to change L2VPN BGP nexthop to secondary IP on tailend and I am not sure if it is possible using policy, usually L2VPN takes remote router-id as nexthop.

     


    @sebastianw wrote:

    5) Why is that? If I build a RSVP path to the new Loopback IP it won't be used for all the other stuff, will it?

     

     


    See above, secondary IP is not inserted into TED by default.

    HTH

    Thanks

    Alex



  • 5.  RE: Use RSVP only for ONE l2circuit

    Posted 07-01-2013 07:04

    @aarseniev wrote:

    Secondary IP is not inserted into TED by default. You can estalish a RSVP LSP to secondary IP only if You disable CSPF.

    Or You can use "no-install-to" and "install <secondary IP/netmask>" knobs under LSP stanza, to force installation of secondary IP into inet.3

    But then You have to change L2VPN BGP nexthop to secondary IP on tailend and I am not sure if it is possible using policy, usually L2VPN takes remote router-id as nexthop.

     


    Hi,

     

    thanks for your answer. I think I probably wasn't clear, we're using l2circuit, not l2vpn. I disabled the cspf in the lsp. As I see it now I would just add another loopback IP on both ends and add this to the IGP. Then I would build my RSVP path between these with strict path options. Would that work?



  • 6.  RE: Use RSVP only for ONE l2circuit

    Posted 07-01-2013 07:56

    Hello,

    AFAIK, in general You need CSPF _ON_ to use explicit paths (strict or loose, does not matter).

    You may get by with CSPF _OFF_ & explicit paths only in some simple topologies like triangles or rings.

    HTH

    Thanks

    Alex



  • 7.  RE: Use RSVP only for ONE l2circuit

    Posted 07-02-2013 01:34

    @aarseniev wrote:

    Hello,

    AFAIK, in general You need CSPF _ON_ to use explicit paths (strict or loose, does not matter).

    You may get by with CSPF _OFF_ & explicit paths only in some simple topologies like triangles or rings.

    HTH

    Thanks

    Alex


     

    Hello,

     

    we don't have TED information in OSPF so I can't use CSPF anyway. The goal *is* to have an explicit configured path. Reading the Juniper documentation that's what no-cspf is for. Or does it have other sideeffects?



  • 8.  RE: Use RSVP only for ONE l2circuit

    Posted 07-02-2013 04:42

    Hello,

     


    @sebastianw wrote:

     

    we don't have TED information in OSPF so I can't use CSPF anyway. The goal *is* to have an explicit configured path. Reading the Juniper documentation that's what no-cspf is for. Or does it have other sideeffects?


    Plenty. Just a few which immediately came to my mind -

    with CSPF _OFF_ You won't be able to use:

    1/ admin-groups/"link-colouring",

    2/ automatic bypasses/detours (only manual), 

    3/ TE metric

     

    HTH

    Thanks

    Alex



  • 9.  RE: Use RSVP only for ONE l2circuit

    Posted 07-02-2013 06:22

    @aarseniev wrote:

    Plenty. Just a few which immediately came to my mind -

    with CSPF _OFF_ You won't be able to use:

    1/ admin-groups/"link-colouring",

    2/ automatic bypasses/detours (only manual), 

    3/ TE metric



    Hi, that's okay, that is exactly what we want. 🙂 We want a RSVP LSP over *one* path that breaks when that path is not available. We need none of this features.

     

    Still, I ended up using MPLS CCC with remote-switch-interface as l2circuit will not work over a secondary loopback IP. Works just fine for us.



  • 10.  RE: Use RSVP only for ONE l2circuit

     
    Posted 07-01-2013 06:55

    Try mpls lsp tunnel cross connects: http://www.juniper.net/techpubs/en_US/junos10.4/topics/usage-guidelines/mpls-configuring-mpls-lsp-tunnel-cross-connects-using-ccc.html

     The RSVP-TE LSPs configured under "remote-interface-switch" are dedicated for ccc .

     

    Krasi



  • 11.  RE: Use RSVP only for ONE l2circuit

    Posted 07-01-2013 07:05

    @Krasi wrote:

    Try mpls lsp tunnel cross connects: http://www.juniper.net/techpubs/en_US/junos10.4/topics/usage-guidelines/mpls-configuring-mpls-lsp-tunnel-cross-connects-using-ccc.html

     The RSVP-TE LSPs configured under "remote-interface-switch" are dedicated for ccc .

     

    Krasi


    Wouldn't that suffer from the same problem the l2circuit has (namely that the active path would be LDP not RSVP)?



  • 12.  RE: Use RSVP only for ONE l2circuit

     
    Posted 07-02-2013 00:25

    You can leave these dedicated LSPs with default preference 7 - their remote next-hops wouldn't appear  in inet.3 table and wouldn't affect other services. 

     

    Krasi