Re: Service Instances and bridge domains MTU

I think I may have unicast this back to Carlos by accident. here is my
response for clarification on the issue. Thanks all.

Eric

If this turns out
to be a double post I apologize.

________________________________
 From:
Eric campbell <ericwcampbell_at_yahoo.com>
To: Carlos G Mendioroz
<tron_at_huapi.ba.ar>
Sent: Saturday, May 11, 2013 8:57 AM
Subject: Re: Service
Instances and bridge domains MTU
 

Carlos,

Thanks for getting back to me.
This is rather simple 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

Eric

As far as I can tell this was a new post with a
new problem. If somehow I emulated an existing thread then it was completely
accidental.

________________________________
 From: Carlos G Mendioroz
<tron_at_huapi.ba.ar>
To: Eric campbell <ericwcampbell_at_yahoo.com>
Sent:
Saturday, May 11, 2013 8:28 AM
Subject: Re: Service Instances and bridge
domains MTU
 

Eric,
just to be clear, the ping works if DF bit is not set ?
So someone is doing PMTU discovery since the ASR is only bridging.
Would you
share the whole topology and how you did determine that the
ASR is the one
filtering large frames ?

BTW, starting a new thread by replying an old one
leaves headers
(References) that mail user agents use to missplace your post
:(

-Carlos

Eric campbell @ 11/05/2013 08:01 -0300 dixit:
> 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 momment 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.
>
> Thanks to all,
> Eric
>
>
> Blogs and organic groups at http://www.ccie.net
>
>
Received on Sat May 11 2013 - 06:01:33 ART