VLAN Troubles

Aled Morris aledm at qix.co.uk
Tue Mar 6 12:04:38 CST 2012


"show vlan" will tell you if the VLAN has been created on the Cisco.

The config to create it is easy (and necessary):

!
vlan 25
 name Radiology
!

Aled


On 6 March 2012 17:55, Jason Baugher <jason at thebaughers.com> wrote:

> +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.
>>>
>>>
>>>
>>
>
>


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