Dot1q

[jeaton]

I have a 1921 configured to do Dot1Q encapsulaton

I have two network which I control with the Dot1q

I have been using switches ver 12.2 3560 which support the Dot1q encapsulation

I have just purchased a C2950tt-s  ver 12.2 which doesn't have the option for

"switchport trunk encapsulation dot1q"

Is there an option to turn this on, or is ther another way of setting this up?

[John Blakley]

Joe,

The two types of encapsulation were ISL and dot1q. The later model switches don't support ISL because Cisco is moving away from it (it was Cisco proprietary). If you don't have the option, the dot1q is already supported. To see this, you can do a "show int trunk" and you would see "n-802.1q" or just "802.1q" in the column.

HTH,

John

[jeaton]

When I do the show int trunk it return nothing

[John Blakley]

That just means you don't have a trunk established with another switch yet. Do you have this one connected to another switch?

[jeaton]

No its connect to a 1921 router doing the Dot1q

Here's a show int trunk were both the switch and router are config for Dot1q

Port        Mode         Encapsulation  Status        Native vlan
Fa0/46      on           802.1q         trunking      1

Port        Vlans allowed on trunk
Fa0/46      1-4094

Port        Vlans allowed and active in management domain
Fa0/46      1-2

Port        Vlans in spanning tree forwarding state and not pruned
Fa0/46      1-2

[John Blakley]

Joe,

The router connects to the switch? You'd need to trunk the port on the switch manually because routers don't support DTP. The information that you just posted indicates (Mode on) that it's a static trunk. You can do this with "switchport mode trunk" on the interface that the router connects to and you should be set.

HTH,

John

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[Abzal]

Hi,

If both side of switches configured correctly with trunk we able to see by command

sh int trunk

To see which VLANs are allowed through trunk and native VLAN, and trunk protocol such as dot1q.

Both sides must have same native vlan and trunking protocol.

Hope it will help.