From: MADMAN (dmadlan@qwest.com)
Date: Tue May 11 2004 - 12:00:03 GMT-3
Howard C. Berkowitz wrote:
> At 1:00 PM +0530 5/11/04, Sachin Shenoy wrote:
>
>> Hi,
>>
>> I was wondering if trunking over WAN is possible ...
>> What I mean by that is
>>
>>
>> Serial Link
>> SW1----R1<------------->R2--SW2
>>
>> Is it possible to trunk VLANs from SW1 to SW2 ???
>> (So LAN IP ranges for VLANs on SW1 and SW2 will be the same !)
>
>
> In certain, restricted, cases, usually requiring gigabit or faster
> transmision media, yes. See such things as Private VLAN Service (more
> the IETF term) and QinQ encapsulation (although the latter is not a WAN
> protocol, but the distinction between LAN and WAN is less and less
> useful). It's also possible using MPLS.
Not that restricted actually and on speeds as low as 100M. We are
rolling out a new service that will provide this using 6500s in the core
and 3550's at the customer site, MPLS is also being used. The customer
can route, trunk or whatever they desire.
Dave
>
> Why do you consider this a good idea? It has potential scalability
> issues, for example, involving both absolute delay greater than expected
> by LAN devices. Another scalability issue is that uncontrolled growth
> at both locations may cause the safe number of devices in a broadcast
> domain to be exceeded.
>
> I've been asked to do this many times, on the basis that "layer 2 is
> simpler." At a certain level of scaling, it is not. In general, in the
> circumstance you describe, I'd route between the sites without
> overwhelming evidence to the contrary. I can even keep VLAN numbers
> consistent at both sites.
>
> Unfortunately, studying for the CCIE lab overempasizes lots of things
> that may be possible, but not a good idea in the real world.
>
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-- David Madland CCIE# 2016 Sr. Network Engineer Qwest Communications 612-664-3367"Emotion should reflect reason not guide it"
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