[c-nsp] Low end cisco switch that supports dot1q tunneling and design question

[Per Carlson]

Hi.

> Also, can the tunnel terminate on multiple
> switches if they are all configured with the same access vlan tag?

Yes, but not with out some gotchas.

If you have a lot of broadcast traffic, and are running the inner
Vlans (C-Vlans) "sparsely meshed" you will have a lot more broadcast
traffic than in a normal flat dot1q-domain.

As the "tunneling switches" have no knowledge of the inner Vlans
(C-Vlan), broadcasts are flooded on all ports *even if a C-Vlan
doesn't exist on a certain port*. In other words: if Vlan X is
deployed between port A and B, Vlan Y between A and C, (and no other
Vlans exists,) all broadcast traffic entering port A on Vlan X will be
flooded on both port B and C (on Vlan X).

If there are more than three ports in the domain, things just get worse...

If all C-Vlans are to be found on all ports ("fully meshed"), this
drawback doesn't matter, the broadcast had to be flooded to all ports
anyway.

-- 
Pelle

RFC1925, truth 11:
 Every old idea will be proposed again with a different name and
 a different presentation, regardless of whether it works.