Re: OT: Layer 2 over Layer 3 for SPAN (Voice Recording)

From: Dale Shaw <dale.shaw_at_gmail.com>
Date: Mon, 2 Nov 2009 14:57:50 +1100

Hi,

On Sun, Nov 1, 2009 at 10:13 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar> wrote:
>
> Just an idea that popped in my mind: what about keeping L2 just for
> an RSPAN vlan ?
> I.e., make your DA (distribution access) links L2 trunks, have your L3
> traffic into a dedicated vlan (SVIs) and create the RSPAN vlan.

As much as I love "no switchport", I agree that what Carlos is
proposing is a very feasible solution, and doesn't significantly
change your logical or physical topology. I've used this before, and
even retro-fitted it into an existing network, where L2TPv3 etc.
weren't options due to deployed platforms.

If the requirement wasn't cross-campus, and cabling up some dedicated
links was cheap/easy, you could create a dedicated L2 network for this
purpose. It sounds like that wouldn't be the case for you, though.

- Use a dedicated "L3" VLAN ID for every point-to-point link
- Disable STP for each VLAN used for this purpose
- Configure switchports as trunks and permit only the (common) RSPAN
VLAN ID, and the dedicated "L3" VLAN ID
- Ensure the dedicated "L3" VLAN ID is pruned off all other trunk links

cheers,
Dale

Blogs and organic groups at http://www.ccie.net
Received on Mon Nov 02 2009 - 14:57:50 ART

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