Re: MPLS VPN Label

A traceroute from CE1 to CE2 should reveal both the IGP and VPN labels.

7600_CE2#traceroute ipv6

Target IPv6 address: 2013::1
Source address:
Insert source routing header? [no]:
Numeric display? [no]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Priority [0]:
Port Number [0]:
Type escape sequence to abort.
Tracing the route to 2013::1

  1 2010:1::1 0 msec 0 msec 0 msec
  2 ::FFFF:44.1.1.1 [MPLS: Labels 16013/20077 Exp 0] 28 msec 28 msec 0 msec
  3 ::FFFF:18.1.1.2 [MPLS: Labels 16018/20077 Exp 0] 4 msec 0 msec 4 msec
  4 ::FFFF:77.1.1.2 [MPLS: Labels 24524/20077 Exp 0] 24 msec 0 msec 0 msec
  5 ::FFFF:88.1.1.2 [MPLS: Label 20077 Exp 0] 28 msec 0 msec 0 msec
  6 2011::2 0 msec 0 msec 0 msec
7600_CE2#

Regards,
Naveen.
CCIE #25432

On Fri, Jun 24, 2011 at 1:15 PM, Brian McGahan <bmcgahan_at_ine.com> wrote:

> The prefix itself doesn't have two labels, the actual packets in the
> data plane will have two (or more) labels. The VPN label is the bottom-most
> label, not the top label. The top label is usually the transport label that
> is derived from LDP. In short the transport label tells the MPLS cloud
> which PE router the packet is destined to, then once it arrives there the
> VPN label tells the PE which CE facing interface the packet is destined to.
>
> On the PE routers you can see what the VPN label is by issuing the
> "show bgp vpnv4 unicast all w.x.y.z", where w.x.y.z is the VPNv4 prefix in
> question. In the actual MPLS cloud you can see both the transport (topmost)
> label and the VPN label by looking at the "debug mpls packet" output.
>
> "untagged" and "no label" mean the same thing, that the packet will
> be forwarded out an interface that is not running MPLS, or does not have a
> label binding to that prefix. For the PE to CE link this is normal, because
> the CE is not running MPLS.
>
> For more detail check this video on MPLS Layer 3 VPN Verification &
> Troubleshooting: http://goo.gl/Ys0lF
>
> HTH,
>
> Brian McGahan, CCIE #8593 (R&S/SP/Security)
> bmcgahan_at_INE.com
>
> Internetwork Expert, Inc.
> http://www.INE.com
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Naufal Jamal
> Sent: Friday, June 24, 2011 2:26 PM
> To: ccielab_at_groupstudy.com
> Cc: rahula_at_hcl.com
> Subject: MPLS VPN Label
>
> Hi,
> I have set up a MPLS VPN network and my end-to-end ping works fine over the
> MPLS. Ie I can ping CE1 from CE2 and vice-versa. I need to understand few
> things regarding MPLS VPN label.
> It was written on the books that the prefixes carry two labels with them
> while
> traversing through the MPLS network with VPN label being on the top. Can we
> see the VPN label for any prefix in the P routers?
> PE1(config-router)#do sh mpls forwarding-tableLocal Outgoing Prefix
> Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id
> switched interface19 Untagged 1.1.1.1/32[V] 3762 Fa0/0
> 10.10.10.1
> Why the outgoing tag is mentioned as Untagged. 1.1.1.1 is my route in CE1
> router which is inside the vrf.
> PE1(config-router)#do sh ip bgp vpnv4 all labels Network Next Hop
> In label/Out labelRoute Distinguisher: 100:100 (ABC) 1.1.1.1/32
> 10.10.10.1 19/nolabel
> Why is "nolabel" mentioned as the Out label here?
> Please help me understand.
>
>
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Received on Fri Jun 24 2011 - 13:23:47 ART