Routing Question on 6509

[Ryan Fisher]

So, this may be a newbie question, but I'm trying to figure something out.  I’m working on putting our old 6509 in the lab, so I cleared some of the config off of it to start fresh.  As I’m creating new vlans, I’m assuming that they’re supposed to create the connected routes when the vlan interfaces come up.  However, they’re only being created when something comes up that’s on that network.  Being that this is just getting going, I don’t have anything plugged in to it yet.  I went down with my laptop and started to plug things in and I could see the connected routes being created, but then would disappear when I removed it from that network.

Is that how it’s supposed to work?  My assumption was that when you bring up the layer 3 vlan interface it should create those connected routes right away.  That’s how it’s always worked before, and that’s how it works now on the new network.  It was doing this on the 6509 even before I cleared the config on it, when it had its old configuration.  On our new network with VSS 6506's, I can create a new layer 3 vlan and it creates the connected route right away and I can ping it, just like the 6509 did in the past.

If anyone can help me understand this, I would appreciate it.  Let me know if you want me to post its config.

Thanks!

[lgijssel · Accepted solution]

When the last interface in a vlan goes down, the vlan goes down also. That's how it always worked.

The reason why this does not occur often in a live network is that in almost 100% of the normal networks, you have a trunk which is carrying the vlan.

The trunk also counts as an interface in the vlan. As long as this trunk stays up, the vlan remains active (up) as well.

regards,

Leo

[Ryan Fisher]

Ahh, ok.  So that makes sense that the trunks kept the vlans active.  So, technically, if I create a trunk to another switch it should then create all my connected routes?  Can I configure a trunk port on the 6500 and not connect anything physically?  Or does there have to be a physical connection for that trunk to keep the routes up?

One other question, though, when you said "When the last interface in a vlan goes down, the vlan goes down also."  you meant the physical connection of the client to the switch on that vlan, right?  Because I could read this as the vlan interface itself, but I don't think that's what you mean.

Thanks for the info, though.  That helped a lot!

[Jon Marshall]

Ryan

Correct, if you had an active trunk link which allowed all the vlans that you had L3 vlan interfaces for then it would create the connected routes in the routing table. The trunk link would have to be active though ie. you couldn't just create a trunk and not connect that link to another switch, the trunk port needs to be up/up.

Yes, Leo meant when the last active port, either a port in the vlan or a trunk with that vlan on it goes down the L3 vlan interface goes down.

Jon

[Ryan Fisher]

Thanks a lot!  You guys completely answered my questions.  I've got it up and running now and started to connect things to it, and it's working like it should.

Thanks!