[AusNOG] Running out of VLANs

[Lincoln Dale]

1. Sounds like you're running per-VLAN spanning tree.  That won't scale.
Investigate MST instead.

2. Friends don't let friends run large L2 networks to start with. its a
large shared-fate fault domain and doesn't really scale that well.

3. Cisco doesn't put catalyst 3750s in data centre designs and for good
reason. It may be the 'best' of the C3K family but as you've found its
restricted to 1K VLANs.  There isn't a SDM Template that increases this.

4. Dare I suggest it but investigate alternatives to this. There's no
reason in 2013 to have blocked links, pretty much every vendor has a
MLAG-like thing, even Cisco, just not on C3K.

Other people here are suggesting q-in-q. I'd suggest against that. Reality
is you have a switch with an anemic MAC table size and all you're doing is
making troubleshooting harder doing that.  Hitting VLAN limits implies
you're doing "VLAN per customer", in its default SDM template its a 6K MAC
table, with "router per customer" and 1 VM per customer you're at 2 MAC
addresses/VLAN so likely you're already well on the way to exhausting the
MAC table since its not a perfectly utilized resource.


cheers,

lincoln.



Lincoln Dale | Principal Engineer, Arista Networks Inc. |
ltd at aristanetworks.com
au did: +61 3 9999 7442 | m: +61 417 457 965 | us did: +1 408 547 5782


On Mon, Dec 16, 2013 at 2:20 PM, James Mcintosh <
james.mcintosh at rocketmail.com> wrote:

> Hi Noggers,
>
> What are people doing about hitting switch VLAN limits? We terminate a lot
> of Ethernet services from several carriers. Our Cisco switch gear is great
> but limited to 128 spanning tree VLAN sessions and 1,000 VLANs.
>
> We've long since passed the 128 per-VLAN spanning tree limit. We're now
> getting closing in on 1,000 VLANs.
>
> I'm sure there are service providers on list who are much larger than we
> are and have solved this problem.
>
> Would love to hear thoughts on the best approach.
>
> Just to give a bit more detail - we aggregate all our upstream carrier
> circuits on the Cisco switch then trunk the customer VLANs to the
> appropriate router for termination.
>
> -James
>
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> AusNOG at lists.ausnog.net
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>
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