Re: incoming tagged vlans through 2 3550

WAYNE MOORE · ‎02-27-2004

I am changing out 2 RJ lynx dumb fiber converters to something managable, 2 3550s.

so in the 3550s I am using switch 1 fa0/1 in, gig0/1 out.. Switch 2 gig0/1 in from switch one and fa0/1 out.

config

switch 1

fa0/1

switchport trunk encap dot1q

swtichport mode trunk

gi0/1

switchport trunk encap dot1q

swtichport mode trunk

switch 2

gi0/1

switchport trunk encap dot1q

swtichport mode trunk

fa0/1

switchport trunk encap dot1q

swtichport mode trunk

and it is not letting anything tagged traffic through.

please let me know if you can see the err of my ways..

greatly appreciated.

p.s. for fun I also tried this config..

switch 1

fa0/1

switchport access vlan 6

swtichport mode access

gi0/1

switchport trunk encap dot1q

swtichport mode trunk

switch 2

gi0/1

switchport trunk encap dot1q

swtichport mode trunk

fa0/1

switchport access vlan 6

swtichport mode access

but that didnt work either, although I really didnt know if 3550s do q in q...

smcquerry · ‎02-27-2004

In order for a Cisco switch to pass tagged traffic, the VLAN must exist on all the switches in the path. So let's say that you have traffic tagged with VLAN 10, 20, and 30. You would need to create these vlans on each switch in the path.

This can be done using the vlan command in global configuration mode.

Config t

Switch(config)#vlan 10

Switch(config-vlan)#vlan 20

Switch(config-vlan)#vlan 30

Switch(config-vlan)#end

Switch#copy run start

You will have to configure all of the VLANs on each switch.

If you don't want to have to continually create VLANs for this switch you can manually configure Q-in-Q tunneling. This may be your best option. To do this, try the following configuration.

switch 1

config t

vlan dot1q tag native

interface fa0/1

swtichport mode dot1q tunnel

interface gi0/1

switchport trunk encap dot1q

swtichport mode trunk

switch 2

config t

vlan dot1q tag native

interface gi0/1

switchport trunk encap dot1q

swtichport mode trunk

interface fa0/1

swtichport mode dot1q tunnel