MTU and Domain groups

First I would apologize to the other poster for inadvertently Hijacking his
thread.

I will start a new thread at this point and maybe That will work.
Folks,
 
  I just want to start off by saying thanks to all of the
 regulars
in the group for the consistent knowledge sharing.
 
  I am a long time
Lurker, but I have stumbled onto something which has me puzzled to say the
least.
 
  I am attempting to create a bridge domain between two interfaces on
an ASR 1006 and am running into a strange MTU issue.
 
 
 Everything is
working fine I am tunneling my q-in-q/802.1q traffic
popping and pushing the
necessary tags and what not, however when I try
to ping accross it using a
1500 byte packet with the df bit set i
cannot. I can ping across it with a
1400 byte packet but of course this
is not the magic number.
 
  I have tried
setting the MTU at the
interfaces involved (gig interfaces) but cannot for
the life of me
figure out why this is happening. This happens with a single
tag as well
 as a stack of them. I do not have a BDI interface at the moment,
but I
am not sure i really need one since I am transiting the box. The only
thing that i am able to think of at the moment is some sort of system
wide
MTU setting. This may become a no duh moment for me in the end, but
 I cannot
find the command if it exists. Any guidance would be
appreciated. If there is
any information that is lacking let me know and
 i will get it out here.
This is a rather small test environment at the moment.

I have an Adtran 8044
- directly to the ASR on gig 0/1/1 the ASR then bridges this traffic to the
interface Gig 0/1/2 - which then places it on the wire as a single tagged
trunk going into a 6509 trunk port and finally terminating on an SVI. On the
other side of the Adtran is a simple laptop connected to the 8044 which is
where I am originating the 1500 byte pings that terminate to the SVI on the
6509.

The 8044 simply takes the packet in as a native packet in this case,
applies a 802.1q tag to it, and then ships it out a trunk port to the ASR.
The 8044 has a MTu set at 2000 on this port, The ASR has an interface level
MTU of 1600 and the 6509 has an MTU of 1500. Also I have tried it with the MTu
set at Max on the 6509 as well. Like I said I am sure that in a setup as small
as this the answer is staring me in the eye.

Since the 6509 is receiving a
trunk port off of the ASR with a single tag applied I feel the problem is
probably not there. The Adtran takes the taffic in from the laptop at 1500 MTU
and then applies its tag then shipping it out.

I have also tried performing
this ping from a 7206 I have that is spare set up like the laptop in this case
using the same parameters.

Thanks for assisting

 
 
  Thanks to all,
  Eric

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Received on Sun May 12 2013 - 09:02:54 ART