Trouble with mpls vpn and P router

nompanemnompanem Posts: 6Member ■□□□□□□□□□
Hi,
I've configured a basic topology with 2 PE routers, 1 P router and a CE for every PE. The protocol running PE-CE is RIP configured for VPN, with redistribution into MP-BGP. The IGP in the core is OSPF. When I connect the PE's directly I get ping from CE to CE, but when I connect them through the P router I can't seem to get connectivity even though I do get the correct routes on both CE's, which means BGP is configured correctly and redistributing. When I check the mpls forwarding-table on the P router I see only labels towards the loopbacks of the PE's and no entry for the tag which I see on the PE's ( tag 20).
Does anyone have an idea how should I troubleshoot this issue? I've gone through the MPLS and BGP configuration for both the PE's and P and I've found nothing. I've even tried changing the source of the BGP updates but to no avail.
Thanks in advance for any assistance

Comments

  • SteveO86SteveO86 Posts: 1,423Member
    I'd post the configs so we can take a look icon_smile.gif
    My Networking blog
    Latest blog post: Let's review EIGRP Named Mode
    Currently Studying: CCNP: Wireless - IUWMS
  • nompanemnompanem Posts: 6Member ■□□□□□□□□□
    Your'e right. I'll post them next time. For now I've found the problem with my config, I forgot to make the loopbacks ospf point-to-point.
    Thanks
  • SteveO86SteveO86 Posts: 1,423Member
    Awesome!

    It's always the small details that get you icon_smile.gif
    My Networking blog
    Latest blog post: Let's review EIGRP Named Mode
    Currently Studying: CCNP: Wireless - IUWMS
  • rwestphalrwestphal Posts: 3Registered Users ■□□□□□□□□□
    There probably something wrong with your LDP configuration.

    " When I check the mpls forwarding-table on the P router I see only labels towards the loopbacks of the PE's and no entry for the tag which I see on the PE's ( tag 20)."

    This is _weird_ but it wouldn't be a problem if you
    changed the source of the BGP Updates to your loopback interfaces...
  • Forsaken_GAForsaken_GA Posts: 4,024Member
    rwestphal wrote: »
    There probably something wrong with your LDP configuration.

    " When I check the mpls forwarding-table on the P router I see only labels towards the loopbacks of the PE's and no entry for the tag which I see on the PE's ( tag 20)."

    This is _weird_ but it wouldn't be a problem if you
    changed the source of the BGP Updates to your loopback interfaces...

    It's not at all weird when using OSPF at the core IGP. The problem comes from the fact that there's a discrepancy between the routing table and the prefix the interface is actually configured with. LDP will advertise a label for the prefix on the interface (probably a /24 I'm guessing), but OSPF will advertise the loopback as a /32 by default. LDP finds no prefix in the routing table to match it to, so no label gets advertised.

    So either change the network type to point-to-point to get the true prefix advertised into OSPF, or do smart IP management and actually address your loopbacks with /32 masks.
  • nompanemnompanem Posts: 6Member ■□□□□□□□□□
    As my previous post says, your completely right and that was the cause of the problem. Next time I'll be more carefull
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