Re: MPLS VPN Label

When doing a tracert from CE2 to CE1 its showing me only one label which i
think is the VPN label
CE2(config-router)#do trace 1.1.1.1
Type escape sequence to abort.Tracing the route to 1.1.1.1
  1 30.30.30.2 236 msec 68 msec 40 msec 2 10.10.10.2 [AS 100] [MPLS: Label 19
Exp 0] 256 msec 172 msec 184 msec 3 10.10.10.1 [AS 100] 280 msec * 196 msec
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] 8814 Fa0/0
 10.10.10.1
and the P router (which sits in the middle of PE1 and PE2). This is where I am
getting confused. P-PE1-PE2 are running bgp vpnv4 and ospf amongst them.
1.1.1.1 is on CE1. LDP is up and running on all three of them and neighborship
is up.
P(config-router)#do sh ip bgp vpnv4 all 1.1.1.1% Network not in table

--- On Fri, 24/6/11, Naveen <navin.ms_at_gmail.com> wrote:

From: Naveen <navin.ms_at_gmail.com>
Subject: Re: MPLS VPN Label
To: "Brian McGahan" <bmcgahan_at_ine.com>
Cc: "Naufal Jamal" <naufalccie_at_yahoo.in>, "ccielab_at_groupstudy.com"
<ccielab_at_groupstudy.com>, "rahula_at_hcl.com" <rahula_at_hcl.com>
Date: Friday, 24 June, 2011, 8:23 PM

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 Sat Jun 25 2011 - 02:20:05 ART