VLAN Troubles

Tue Mar 6 17:55:31 UTC 2012

+1 on show interface trunk, which will probably tell you that only vlan 
1 is allowed on your trunk interfaces.

I find it easy to forget that a Cisco switch will not pass tagged 
traffic for a vlan if that vlan isn't created on the switch. Even if you 
do something like "switchport trunk allow vlan 12" on a trunk port, it 
won't create the vlan on the switch unless you specifically create it or 
you add it to an access port like "switchport access vlan 12".

Jason

On 3/6/2012 11:04 AM, Greg T. Grimes wrote:
>
> On the cisco, do a 'show interface trunk'.  Be sure that it thinks 
> it's supposed to pass those VLANs.  Make sure "Vlans allowed on trunk" 
> includes the VLAN.  Same for "Vlans allowed and active in management 
> domain".  Then the important one is "Vlans in spanning tree forwarding 
> state and not pruned".  If it's not there then it's being pruned.  
> Also on your Dell uplink add the following line to the uplink port:
>
> switchport access vlan add 12,22
>
> See what that does for you.
>
> On Tue, 6 Mar 2012, Alan Bryant wrote:
>
>> I hope everyone is having a better workday so far than I am.
>>
>> I am trying to clean up the network for the Hospital I work for, and
>> part of that is creating two VLAN's for two separate subnets on our
>> network. Before, it was not separated by VLANs. We are also replacing
>> our aged Juniper firewall with an ASA.
>>
>> I'm very new to VLAN's, so I am hoping this is something simple that
>> you guys can help me out with.
>>
>> We have two switches that do not seem to be passing VLAN traffic. The
>> two switches are a Dell Powerconnect 5324 & a Cisco 3560G. The Cisco
>> switch appears to be functioning fine, but the Dell switch is only
>> passing traffic to the Cisco that is on the default untagged VLAN1.
>> Our second VLAN is not getting passed to the Cisco at all, I am not
>> seeing any packets tagged with the particular vlan in Wireshark.
>>
>> I have Port 1 on the Dell switch connected to port 29 on the Cisco
>> switch, and port 1 on the Cisco switch connected to the ASA.
>>
>> I have the following config on the relevant ports on the Cisco switch:
>>
>> interface GigabitEthernet0/1
>> description ASA 5505
>> switchport trunk encapsulation dot1q
>> switchport mode trunk
>>
>> interface GigabitEthernet0/29
>> description Radiology Switch
>> switchport trunk encapsulation dot1q
>> switchport mode trunk
>>
>> Here is the config for the Dell switch:
>>
>> interface ethernet g1
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g2
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g3
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g4
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g5
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g7
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g9
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g10
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g12
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g14
>> speed 1000
>> duplex full
>> exit
>> interface ethernet g15
>> speed 1000
>> duplex full
>> exit
>> port jumbo-frame
>> interface ethernet g1
>> switchport mode trunk
>> exit
>> interface ethernet g24
>> switchport mode trunk
>> exit
>> vlan database
>> vlan 12,22
>> exit
>> interface range ethernet g(2,4,7,12,14-15)
>> switchport access vlan 12
>> exit
>> interface vlan 12
>> name Radiology
>> exit
>> interface vlan 22
>> name Guest
>> exit
>> interface vlan 1
>> exit
>>
>> Anyone have any ideas or pointers? Is there more information that I
>> need to provide? Vlan1 works just fine, of course. It is Vlan 12 that
>> is not working. Everything on the Dell switch is communicating with
>> each other just fine on the same subnet.
>>
>>
>