From: Don (seadon@attbi.com)
Date: Sun Oct 13 2002 - 23:24:15 GMT-3
I'm sorry hsb, you are correct. I reviewed my notes and discovered what it
was that I remembered having done. I wanted to transport a trunk over a T1
line to backup a trunk over 100mbit Ethernet over fiber. I had 2501's to
act as T1 interfaces, so I tested using bridging from a 3524XL-EN trunking
interface to the Ethernet interface of the 2500 to the T1 interface of the
2500 and back again at the far end. It almost worked, both ISL and dot1q
trunks were carried across the T1, except that frames were truncated to
normal Ethernet size limits instead of ISL or dot1q size limits due to the
Lance hardware used on the Ethernet interface. So full size packets would
not work, but if I limited the MTU to the smaller size, it worked perfectly.
It is 10mbit interfaces on 2600's that will do dot1q but not ISL.
Don
----- Original Message -----
From: "Hansang Bae" <hbae@nyc.rr.com>
To: <ccielab@groupstudy.com>
Sent: Sunday, October 13, 2002 11:27 AM
Subject: Re: router on a stick
> At 07:35 AM 10/11/2002 -0700, Don wrote:
> > You can not do ISL on a 10mbit interface. You can do dot1q
> >encapsulation. A major problem with doing dot1q encapsulation with a
2500
> >is that the Ethernet interface will then no longer support an MTU of 1500
> >because of a hardware limitation. The maximum MTU needs to be decreased
to
> >something like 1497 (I'm not sure about the exact size but I seem to
> >remember dot1q adds 3 bytes to the frame).
> > Another major problem is that you need at least a 3620 before you
have
> >the necessary mls commands on the router.
>
>
> 2500's CANNOT do ANY type of trunking regardless of IOS. Secondary
addressing will have to suffice.
>
> hsb
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