Re: [mpls-linux-general] MPLS packet capture

[James R. L. <jl...@mi...>]

On Mon, Jun 25, 2001 at 04:44:29PM +0530, JK Swamy wrote:
> Hi all,
> I have configured mpls-linux-0.993 on linux kernel 2.4.5 . I have configured
> two machines

Unfortunately there is a known issue with capturing MPLS packets on
an LER.  Although you should have atleast seen some weird looking ones, if
they are all coming out IP, then something is not working right for you.

So lets verify that MPLS forwarding is occuring first.

(everything I mention below is specific to this setup, I could generalize
but that would make the description more difficult)

Look at /proc/net/mpls_fec is should have (in hex) the IP address of the 
peer. (On A you should see the address for B and on B you should see the
address for A).  In front of the address you should see a hex number.  That
hex number is the 'key' for the out label you've installed.  If you don't
see this information, they that means there is no way for the IP stack to
sent packets to the MPLS stack.

If this info looks right then lets turn to the debugging info.
Turn on MPLS kernel debugging by doing a 'mplsadm -d' (if you do it a second
time it will turn off MPLS kernel debugging). Start sending some packets
via ping.  Stop the ping and look at the output for 'dmesg'.  If you see
info about mpls_output or pushing labels or mpls_input, that means packets
are making it to the MPLS layer.

Lets stop there.  Let me know the results.

Jim

> **************************************************************************
> 
>                                 Manual LSP beteen 2 hosts
>                          ---------------------------
> 
> Setup
> -----
>  ---------             ---------
>  |   A   |             |           |        B         |
>  ---------             ---------
>      |eth0                 |eth0
>      |17.130               |18.114
> -----------------------------------
>          128.104.16.0/22
> 
> Config
> ------
> On A:
>   route add -host B gw B
>   mplsadm -A -B -O gen:16:eth0:ipv4:B -f B/32
>   mplsadm -A -I gen:17:0
> 
> On B:
>   route add -host A gw A
>   mplsadm -A -B -O gen:17:eth0:ipv4:A -f A/32
>   mplsadm -A -I gen:16:0
> 
> On both:
>   mplsadm -L eth0:0
> 
> Now all traffic with destination address of A or B use the LSP.
> 
> I************************************************************************
> 
> I need to use Ethereal 0.8.18 to capture MPLS packets emanating between A and B
> nodes.
> Can anybody tell me why I am not able to see MPLS packets though I am  running
> " ethereal " or "tethereal".
> 
> Yaah ... when I run "mplsadm -d " I am able to see the messages ... but not
> able to make out much from it.
> In /proc/net/mpls_* labeling is ok.
> 
> I would appreciate Ur suggestions.......
> 
> Cheers !!
> --jkswamy
> 
> *********************************
> jkswamy
> Sr. Telecom consultant
> Velankani Information Systems
> ks...@ve...
> ********************************
> 
> 
> 
> 
> 
> 
> 
> 
> ~
> 
> 
> --------------------------------------------------------------
> Velankani Information Systems Ltd, Bangalore, India
> 
> 
> 
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-- 
James R. Leu