Re: [nsp] Routing between VLANs using 802.1q (fwd)

From: Jeff Aitken (jaitken@aitken.com)
Date: Mon Jan 24 2000 - 16:24:26 EST


[Sorry, I responded to the original poster directly, but thought
 this might be helpful to someone else.]

Michael Beckmann writes:
> This is where I have the problem. The switch port is either a trunk, or
> a VLAN member. Example:
>
> > > I also believed that I should set the VLAN of the respective switch
> > > interface to "trunk". Is this not correct ?
> >
> > yes.
>
> Do I have to force it into "trunk" mode ?

Yes, you do. Maybe this example will help. Suppose you've got three
VLANs (10, 11, and 12) that you want to trunk on a single Gigabit
ethernet uplink to your router. For simplicity's sake assume each
VLAN has 10 10/100 switch ports, and uses the 10.10.X.0/24 network,
where X = VLAN number. You'll need to config the router like this:

int gi0/0
descr dot1q trunk for vlans 10-12
!
int gi0/0.10
 descr vlan 10
 encap dot1q 10
 ip addr 10.10.10.1 255.255.255.0
!
int gi0/0.11
 descr vlan 11
 encap dot1q 11
 ip addr 10.10.11.1 255.255.255.0
!
int gi0/0.12
 descr vlan 12
 encap dot1q 12
 ip addr 10.10.12.1 255.255.255.0

And on your switch:

set port name 2/1 vlan10-12 dot1q trunk
set vlan 1 2/1
clear trunk 2/1 2-1005
set trunk 2/1 on 10-12 dot1q

set port name 3/1-10 vlan10
set port name 3/11-20 vlan11
set port name 3/21-30 vlan12
set vlan 10 3/1-10
set vlan 11 3/11-20
set vlan 12 3/21-30
set trunk 3/1-30 off

Keep in mind you might have to disable flow-control negotiation to
get the switch talking to the router (set port negotiate x/y disable)
as this doesn't always work (e.g., between a 12012 and a 6509).

Also, I forget where, but this *is* documented somewhere. I don't
have time right now but I'll look when I get home for the URL.

-- 
Jeff Aitken
jaitken@aitken.com



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