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802.1q header removed in catalyst?

 
 
Roel Villerius
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Posts: n/a
 
      06-15-2006
Hello,

I have question, I'm trying to setup a 802.1q vlan lab envirement. I see
PC 1 sending a ICMP package to the catalyst switch, it includes the 802.1q
bytes. from the switch towards PC 2 I see the ICMP package comming out but
with the 802.1q bytes removed.

On the catalyst I have a simple configuration:

Switch#show running-config
Building configuration...

Current configuration:
!
version 12.0
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Switch
!
!
!
!
!
!
!
no spanning-tree vlan 1
ip subnet-zero
!
!
!
interface FastEthernet0/1
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
switchport trunk encapsulation dot1q
switchport trunk native vlan 666
switchport mode trunk
!
interface FastEthernet0/9
switchport trunk encapsulation dot1q
switchport trunk native vlan 666
switchport mode trunk
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface VLAN1
no ip directed-broadcast
no ip route-cache
!
!
line con 0
transport input none
stopbits 1
line vty 0 4
login
line vty 5 15
login
!
end


What is wrong, the 802.1q bytes should be in the header during the
complete transport? From client till Destination?

Who can help me.


thx.

CU

Roel Villerius
 
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Christophe Fillot
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      06-15-2006
Roel Villerius wrote:

> !
> interface FastEthernet0/8
> switchport trunk encapsulation dot1q
> switchport trunk native vlan 666
> switchport mode trunk
> !
> interface FastEthernet0/9
> switchport trunk encapsulation dot1q
> switchport trunk native vlan 666
> switchport mode trunk
>
> What is wrong, the 802.1q bytes should be in the header during the
> complete transport? From client till Destination?


I suppose that PC1 is sending frames with VLAN 666. You specified on
Fa0/8 and Fa0/9 that the native VLAN is 666, the switch will remove this
tag when forwarding a packet in the native VLAN.

Two solutions to have the tags :
* use another native VLAN (by default it is VLAN 1)
* use "vlan dot1q tag native" to tag the native VLAN.
 
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jw
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Posts: n/a
 
      06-18-2006
vlan header as noted below will be stripped, but would not be if it was an
isl trunk, (native only vlan 1) as far as I recall.

"Christophe Fillot" <(E-Mail Removed)> wrote in message
news:e6smne$jjc$(E-Mail Removed)...
> Roel Villerius wrote:
>
>> !
>> interface FastEthernet0/8
>> switchport trunk encapsulation dot1q
>> switchport trunk native vlan 666
>> switchport mode trunk
>> !
>> interface FastEthernet0/9
>> switchport trunk encapsulation dot1q
>> switchport trunk native vlan 666
>> switchport mode trunk
>>
>> What is wrong, the 802.1q bytes should be in the header during the
>> complete transport? From client till Destination?

>
> I suppose that PC1 is sending frames with VLAN 666. You specified on
> Fa0/8 and Fa0/9 that the native VLAN is 666, the switch will remove this
> tag when forwarding a packet in the native VLAN.
>
> Two solutions to have the tags :
> * use another native VLAN (by default it is VLAN 1)
> * use "vlan dot1q tag native" to tag the native VLAN.



 
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Christophe Fillot
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      06-18-2006
jw wrote:
> vlan header as noted below will be stripped, but would not be if it was an
> isl trunk, (native only vlan 1) as far as I recall.


Indeed there is no concept of native VLAN with ISL. All VLANs are
systematically tagged.
 
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Robert B. Phillips, II
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Posts: n/a
 
      06-20-2006
Keep in mind however, that not all Catalyst switches support ISL.
Newer ones no longer support ISL in favor of 802.1q.

On Sun, 18 Jun 2006 09:27:18 +0200, Christophe Fillot <(E-Mail Removed)>
wrote:

>jw wrote:
>> vlan header as noted below will be stripped, but would not be if it was an
>> isl trunk, (native only vlan 1) as far as I recall.

>
>Indeed there is no concept of native VLAN with ISL. All VLANs are
>systematically tagged.

 
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