[j-nsp] Running OSPF to manage loopbacks, only have trunks

[Morgan McLean]

Thats sort of what I'm expecting. My core is two 8208's running in the same
L2 domain with a trunk between them, and they each connect down to a switch
per cabinet. So switch A cabinet 1 is connected to core-A and switch B in
cabinet 1 is connected to core-B. The machines run bonding and have a drop
on each cabinet switch (which are also trunked over a lag together) so I was
assuming that only one of the cabinet switches will actually have link to
the core at any given time, and the center trunk on the cabinet switches
will always be active, allowing the switch without link to still communicate
through the lag. We don't use RSTP on a vlan basis, but I don't think I have
the need.

Thanks!
Morgan

On Wed, Aug 31, 2011 at 12:12 AM, Chris Kawchuk <juniperdude at gmail.com>wrote:

>
> Chris,
>
> Could you elaborate on:
>
>    Just need to be careful to bridge the VLAN across the trunk link as
> necessary. (i.e. only bridge what you need - switch to switch - don't use
> 'vlan members all').
> What would be the problem if I did all? I might have say tag 2001 going to
> a switch that doesn't play on that vlan, but I wouldn't have problems
> necessarily would I?
>
> Thanks,
> Morgan
>
>
> You're right. It wouldn't necessarily be an issue.
>
> What I'm trying to avoid is bridging VLAN 2001 everywhere (and we're back
> to the original '1 giant LAN' problem).
>
> Switch 1 <> Switch 2 uses VLAN 2001
> Switch 2 <> Switch 3 uses VLAN 2002
> Switch 3 <> Switch 1 uses VLAN 2003
>
> All inter-switch links declared 'family ethernet switching port-mode trunk
> members vlan all'.
>
> Agreed, if switch 3 doesn't have tag 2001 declared, it'll just ignore it /
> not pass it back to switch 1.
>
> However, if you're using a base RSTP topology (VLAN unaware), then one of
> those inter-switch links is going to block.
>
> You will not have routing/IP connectivity on one of the inter-switch links.
> However, this is not necessarily a problem.... If RSTP blocks between a pair
> of switches, OSPF will just lose the inter-switch adjacency - but not
> reachability of each switch in the OSPF database (The Type 1's are all still
> there). The traceroute simply follows the current RSTP forwarding topology.
>
> - Chris.
>
>