From: Ben (ccieben@cox.net)
Date: Tue Mar 14 2006 - 14:36:08 GMT-3
Hi Carlos,
Thanks - you were exactly right... "Router A" was a 2610. I did the
same setup on a 7200 and everything worked as expected.
Thanks!
Ben
Carlos Mendioroz wrote:
> There used to be a problem in some routers with ARP "management" of
> the native VLAN. I Know this happens in 2610s. May be related.
> Debug arp in the router (A) and see if the request/response are "routed"
> to different interfaces (main/.20)...
>
> You may try to move the native vlan config to the main interface
> and see if that helps.
>
> Bottom line, it should work. Native vlan is untagged by default.
> -Carlos
>
> ccieben@cox.net @ 13/3/2006 20:25 -0600 dixit:
>
>> Hello,
>>
>> I have the following attached to a 3550:
>> Port 0/1 - trunked back to a Router A. I am allowing Vlan 10 & 20 & stating that 20 is native.
>> Port 0/5 - a Vlan 20 access port attached to Router B.
>>
>> Router A & Router B are both on the same subnet.
>>
>> With the 3550 in its normal state - Router A & Router B cannot ping each other. Once I add the command:
>> 3550(config)#vlan dot1q tag native
>> Router A & Router B are able to ping each other... I thought that command would only be useful in an SP environment where 1Q/L2 tunneling was being performed.
>>
>> I thought these untagged packets were automatically part of vlan 20? What is the logic of why these devices can't "speak".... can someone help me understand the logic?
>>
>> TIA - Ben
>>
>> ***Router A
>> interface Ethernet0/0.20
>> encapsulation dot1Q 20 native
>> ip address 172.16.17.1 255.255.255.0
>> end
>>
>> ***Router B
>> interface FastEthernet0/0
>> ip address 172.16.17.6 255.255.255.0
>> end
>>
>> ***3550
>> interface FastEthernet0/1
>> description to ROUTER-A
>> switchport trunk encapsulation dot1q
>> switchport trunk native vlan 20
>> switchport trunk allowed vlan 10,20
>> switchport mode trunk
>> end
>>
>> interface FastEthernet0/5
>> description to ROUTER-B
>> switchport access vlan 20
>> switchport mode access
>> end
>>
>> 3550#show int trun
>>
>> Port Mode Encapsulation Status Native vlan
>> Fa0/1 on 802.1q trunking 20
>> <snip>
>>
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>
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