Re: Ping fails across VRF

From: Rick Mur <rmur_at_ipexpert.com>
Date: Sun, 30 Aug 2009 01:36:05 +0200

Yes you have a problem if the Loopback has a /24 mask and you advertise the
/32 in OSPF (like it does by default). That way the router that has the
loopback on it, would advertise a label for the /24 prefix and the upstream
router wouldn't know what to do as it only knows a /32 route.
You solved it by making the interfaces being advertised as /24. Another
option would be making all loopbacks /32.

--
Regards,
Rick Mur
CCIE2 #21946 (R&S / Service Provider)
Sr. Support Engineer  IPexpert, Inc.
URL: http://www.IPexpert.com
On Sun, Aug 30, 2009 at 1:27 AM, Christopher Copley
<copley.chris_at_gmail.com>wrote:
> All,
>
> I finally figured it out.  It appears to be an issue with the Provider
> Backbone in the IGP process.  I am running ospf on the Provider core, and
> ospf was the cause of the issue.   The /32 route by default on a Loopback
> interface was the cause.  The /24 route of the loopback had IMP-NULL, but
> the /32 did not.  I went to the Lo0 of R3 & R6 and made it a p2p interface,
> and it corrected the issue.
>
> Sorry for the long thread, I guess I had to write out the process for my
> head to process.
>
> Thanks,
>
> Chris
>
> On Sat, Aug 29, 2009 at 3:43 PM, Christopher Copley
> <copley.chris_at_gmail.com>wrote:
>
> > Bryan,
> >
> > I tried to remove the Lo0 from IGP and that did not work.   R1/R3 and
> R5/R6
> > are LDP peers.  I have the MP-BGP peering on R3 and R6 via Lo0.  And if I
> > can not get the Lo0 to be a tagged packet then I think I have an IOS bug
> or
> > limitation.   would this be correct.
> >
> > Chris
> >
> >
> > On Sat, Aug 29, 2009 at 3:34 PM, Bryan Bartik <bbartik_at_ipexpert.com
> >wrote:
> >
> >> Chris,
> >>
> >> You are right, you should see "pop" for PHP. If you see untagged this is
> >> because you have not received a label for it. This is why I said check
> your
> >> peerings and make sure CEF is enabled. In some older codes, CEF is not
> on by
> >> default. Are R1/R3 and R5/R6 LDP Peers?
> >>
> >>
> >> On Sat, Aug 29, 2009 at 4:17 PM, Christopher Copley <
> >> copley.chris_at_gmail.com> wrote:
> >>
> >>> Bryan,
> >>>
> >>> This in my Topo...
> >>>
> >>> CE---R3---R1----R5----R6----CE
> >>>
> >>> If I look on R1 to see the ldp forwarding table I see...
> >>>
> >>> Rack2R1#sho mpls forwarding-table | inc (155.2.6.6/32|155.2.3.3/32<
> http://155.2.6.6/32%7C155.2.3.3/32>
> >>> )
> >>> 16     Untagged    155.2.3.3/32      12288      Se0/1/0    point2point
> >>> 18     16          155.2.6.6/32      13036      Fa0/0      150.1.15.5
> >>> Rack2R1#
> >>>
> >>>
> >>> and on R5 I see...
> >>>
> >>> Rack2R5#sho mpls forwarding-table | inc (155.2.6.6/32|155.2.3.3/32<
> http://155.2.6.6/32%7C155.2.3.3/32>
> >>> )
> >>> 16     Untagged    155.2.6.6/32      8973       Fa0/1      150.1.56.6
> >>> 18     16          155.2.3.3/32      16955      Fa0/0      150.1.15.1
> >>> Rack2R5#
> >>>
> >>> If what I have been reading is correct, then R1 and R5 are sending the
> >>> mpls lable as a ipv4 packet to R3 &R6 respectively.
> >>> I have my MP-BGP peerings between R3&R6 via the Lo0 interface.
> >>> I believe that instead of Untagged in the above output I should be
> seeing
> >>> "Pop Label" that is the PHP process, right?
> >>> Then R3 and R6 will untag the packet and direct it to the correct VRF
> and
> >>> an IPv4 packet, Correct?
> >>>
> >>> If the above logic is correct will taking the Lo0 out of my IGP correct
> >>> this issue?  Or is this some strange IOS bug?
> >>>
> >>> Chris
> >>>
> >>>
> >>> On Sat, Aug 29, 2009 at 3:06 PM, Bryan Bartik <bbartik_at_ipexpert.com
> >wrote:
> >>>
> >>>> Chris,
> >>>>
> >>>> You don't need to enable mpls on a loopback. Just out the loopback in
> >>>> your IGP and labels will get advertised. What makes you think PHP is
> >>>> happening to seen? If you see a "no-label" instead of "pop-label" in
> the
> >>>> LFIB, this is not PHP. Make sure you have CEF enabled and your LDP
> peerings
> >>>> are UP throughout the cloud. Let me know what you find.
> >>>>
> >>>> On Sat, Aug 29, 2009 at 3:57 PM, Christopher Copley <
> >>>> copley.chris_at_gmail.com> wrote:
> >>>>
> >>>>> I think I know what is going on....The PHP process is occurring to
> >>>>> soon, by
> >>>>> one router.  I tried to enable mpls ip on the Lo0 interface and get
> an
> >>>>> error...
> >>>>>
> >>>>> % MPLS not supported on interface Loopback0
> >>>>>
> >>>>> Is this an IOS version limitation or a default behavior?
> >>>>>
> >>>>> Thanks,
> >>>>> Chris
> >>>>>
> >>>>> On Sat, Aug 29, 2009 at 2:33 PM, Christopher Copley
> >>>>> <copley.chris_at_gmail.com>wrote:
> >>>>>
> >>>>> > Sorry all pressed send by mistake WAY to early,
> >>>>> >
> >>>>> > Anyway...
> >>>>> >
> >>>>> > I have one VPN and at each of the CE routers I can see the routes
> >>>>> from each
> >>>>> > other across my MPLS backbone.   But ping fails across the Core
> from
> >>>>> CE to
> >>>>> > CE, but the routes are there and look correct.
> >>>>> >
> >>>>> > I have MP-BPG between each PE and the router appear in each VPN.
> >>>>> >
> >>>>> > Any ideas?
> >>>>> >
> >>>>> > Chris
> >>>>> >
> >>>>> >
> >>>>> > On Sat, Aug 29, 2009 at 2:29 PM, Christopher Copley <
> >>>>> > copley.chris_at_gmail.com> wrote:
> >>>>> >
> >>>>> >> Experts,
> >>>>> >>
> >>>>> >> I have an interesting problem with my MPLS study.   I am new to
> MPLS
> >>>>> and
> >>>>> >> MPLS VPNS and I have got to a place where I am stuck.
> >>>>>
> >>>>>
> >>>>> Blogs and organic groups at http://www.ccie.net
> >>>>>
> >>>>>
> _______________________________________________________________________
> >>>>> Subscription information may be found at:
> >>>>> http://www.groupstudy.com/list/CCIELab.html
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>>> --
> >>>> Bryan Bartik
> >>>> CCIE #23707 (R&S), CCNP
> >>>> Sr. Support Engineer - IPexpert, Inc.
> >>>> URL: http://www.IPexpert.com
> >>>>
> >>>
> >>>
> >>
> >>
> >> --
> >> Bryan Bartik
> >> CCIE #23707 (R&S), CCNP
> >> Sr. Support Engineer - IPexpert, Inc.
> >> URL: http://www.IPexpert.com
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
Blogs and organic groups at http://www.ccie.net
Received on Sun Aug 30 2009 - 01:36:05 ART

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