Routing

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How does RSVP discover neighbors?

  • 1.  How does RSVP discover neighbors?

     
    Posted 12-02-2020 05:36
    Hi.

    I noticed that when I configure RSVP on Junos routers, RSVP Hello message unicast to neighbors as shown here: 

    R1 --------------------------------   R2
          .1          10.10.10.0/30          .2


    On R1:
    Dec 2 10:24:56.459181 RSVP recv Hello 10.10.10.2->10.10.10.1 Len=40 lt-0/0/0.1 flags=0x1 ttl=1
    Dec 2 10:24:56.459229 HelloRply Len 12 src-instance 0x78344001, dst-instance 0xde9f0a26
    Dec 2 10:24:56.459238 RestartCap Len 12 restart time 0, recovery time 0
    Dec 2 10:24:56.459247 Capability Len 8 00000018
    Dec 2 10:24:56.459270 RPD_RSVP_NBRUP: RSVP neighbor 10.10.10.2 up on interface lt-0/0/0.1 nbr-type Direct

    We can see from the message above that R2 has sent its RSVP Hello message unicast to R1.

    My question is: How does R2 discover R1's IP address? (I did not see any multicast RSVP packets which could be used for neighbour discovery).


    Many thanks,
    Deepak


  • 2.  RE: How does RSVP discover neighbors?

    Posted 12-02-2020 06:01
    from ted database , which is filled by ospf/isis

    ------------------------------
    Anatoliy
    ------------------------------



  • 3.  RE: How does RSVP discover neighbors?

     
    Posted 12-02-2020 07:49
    Thanks akushner for pointing me in the right direction.

    From my testing, I found that as soon as the OSPF neighborship gets to the 2-Way state, it hands off discovered neighbours to RSVP, which then sends RSVP Hello messages to them. 

    Regards,
    Deepak


  • 4.  RE: How does RSVP discover neighbors?

    Posted 12-08-2020 03:59
    This is the process indeed. RSVP-TE will ship a `hello` packet once OSPF/IS-IS adjacency/neighbor relationship is set between the neighbors. Src/Dst IP information is unicast and will be filled out from the information passed on from IGP.

    Elvin