MTU for ADSL connection

Unanswered Question
Mar 23rd, 2010

Is there a way to set the MTU size for an ADSL connection using an ATM card?

Current output is as follows:

ATM0 is up, line protocol is up
  Hardware is DSLSAR (with Alcatel ADSL Module)
  MTU 4470 bytes, sub MTU 4470, BW 832 Kbit, DLY 610 usec,

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
lkadlik Wed, 03/24/2010 - 06:57

No I dont.  The site this router is in connects to the main office via an mpls connection.  DHCP is not working over the mpls connection even though the helper address in on the lan interface.  I can see the traffic hitting the dhcp server for the dhcp discovery but no offer comes back to the client.  It is weird. All other offices are working over T1 circuits.  The last time I saw weird traffic like this it was due to the mtu size.  I realize it is probably not the case here but thought it might be worth a shot to change it to 1508 on the atm interface.


Paolo Bevilacqua Wed, 03/24/2010 - 07:06

You problem is not due to MTU, beside DHCP packets are very small.

Maybe the DHCP server is just not responding for that subnet.

Try another one or even better, set dhcp server on local router, so even if faulty ciorcuit, you still have service.

lkadlik Wed, 03/24/2010 - 07:12

We plan on trying another subnet this week.  The customer has a new site coming online.  I have already set dhcp to run off the router for the site

I was talking to above.  This should be  a pretty easy set up so I am curious to figure out why it is not working.

lkadlik Wed, 03/24/2010 - 11:23


Yes it does have a return route.  I can do an extended ping from the lan interface of the site to the dhcp server successfully.


This Discussion