Re: Weird MPLS Label Switching Problem

Hi Malik

did you use the no mpls ip propagate-ttl command with the forwarded
keyword ?? ,

if you did then the behaviour you are experiencing is normal as
traceroutes from CE1 to CE2 will not show the hops in the SP core so
it appears to the customer as if they are having a single hop or
better perfromance :) , BUT traceroutes from the PE will shows the
transit P devices as the command with the forwarded keyword only
affects forwarded packets(CE TO CE) not locally generated ones.

Else the next step is to consider the IOS version are you using as
Marko pointed out

On 2/27/11, Marko Milivojevic <markom_at_ipexpert.com> wrote:
> Which IOS are you using?
>
> --
> Marko Milivojevic - CCIE #18427
> Senior Technical Instructor - IPexpert
>
> FREE CCIE training: http://bit.ly/vLecture
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>
> On Sat, Feb 26, 2011 at 22:10, Malik Nouman Ahmad <djmalik_at_gmail.com> wrote:
>
>> What I was trying to tell that the labels are not shown at all with or
>> without "no mpls ip propagate-ttl" command. I know this command is to hide
>> all the hops between PE1 and PE2.
>>
>> When I was not using that command it was showing the hops from
>> CE1->PE1->P1->P2->PE1->CE2 BUT without labels like normal IPv4 traceroute.
>> I
>> used that command just to check if MPLS was working or not, just to be
>> sure
>>
>> The problem is that I cannot see the labels for CE1 to CE2 traceroute at
>> any hop but when I use the same source/destination subnet for tracing from
>> PE1 to PE2 I am able to see label swapping at each hop
>>
>> I hope I am able to describe the problem that I am facing
>>
>> Thanks,
>> Malik
>>
>>
>> On Sun, Feb 27, 2011 at 12:29 AM, Marko Milivojevic
>> <markom_at_ipexpert.com>wrote:
>>
>>>
>>> Which shows you that your "no mpls ip propagate-ttl" did its job and MPLS
>>> backbone is "hidden" from CE devices. Remove this command from PE1, run a
>>> traceroute from CE1 and see the labels re-appear.
>>>
>>> --
>>> Marko Milivojevic - CCIE #18427
>>> Senior Technical Instructor - IPexpert
>>>
>>> FREE CCIE training: http://bit.ly/vLecture
>>>
>>> Mailto: markom_at_ipexpert.com
>>> Telephone: +1.810.326.1444
>>> Web: http://www.ipexpert.com/
>>>
>>> On Sat, Feb 26, 2011 at 21:10, Malik Nouman Ahmad
>>> <djmalik_at_gmail.com>wrote:
>>>
>>>> One thing I forgot to mention. For CE-CE trace there is no label seen in
>>>> the
>>>> traceroute but trace completes properly and I can ping between the CEs
>>>> normally
>>>>
>>>> Thanks
>>>>
>>>> On Sun, Feb 27, 2011 at 12:07 AM, Malik Nouman Ahmad <djmalik_at_gmail.com
>>>> >wrote:
>>>>
>>>> > Hi,
>>>> >
>>>> > I was studying MPLS VPN and while working on an example I am facing
>>>> some
>>>> > strange issue
>>>> >
>>>> > The connectivity is CE1 - PE1 - P1 - P2 - PE2 - CE2
>>>> >
>>>> > PE1(.1) - CE1 (.2) with subnet 172.16.1.0/24 with VRF A (RD=RT=1:1)
>>>> > PE2(.1) - CE2 (.2) with subnet 172.16.2.0/24 with VRF A (RD=RT=1:1)
>>>> >
>>>> > PE1 & PE2 have MPLS VPN set up and I can see labels for everything
>>>> > when
>>>> I
>>>> > check "show mpls forwarding" on the PEs
>>>> >
>>>> > when I trace from PE1 to CE2 I can see labels being switches properly
>>>> using
>>>> > the following command
>>>> > trace vrf A 172.16.2.2 source 172.16.1.1
>>>> >
>>>> > but when trace from CE1 to CE2, there are no labels whatsoever
>>>> > trace 172.16.2.2 source 172.16.1.2
>>>> >
>>>> > Same thing is happening in the reverse direction (i.e. trace from CE2
>>>> to
>>>> > CE1). I have done several examples previously and never faced such
>>>> issue.
>>>> > Instead of doing it all over again I want to troubleshoot the problem
>>>> for
>>>> > learning purpose
>>>> >
>>>> > Can anybody suggest how to troubleshoot this problem? I have applied
>>>> "no
>>>> > mpls ip propagate-ttl" just to see if it was working and it worked
>>>> >
>>>> > Please advise what should I do?
>>>> >
>>>> > Thanks,
>>>> > Malik
>>>>
>>>>
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