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New Member

GigabitEthernet Trunk config

Is the below correct?

This is a trunk 1GB link between 2 sites (C6509 to C3550) and I have found this configured on the interface of the C3550.

Should the 'switchport access vlan 100' be on the C3550?

Thanks

On the C3550

interface GigabitEthernet0/1

description Connection to 1GB Colt

switchport access vlan 100

switchport trunk encapsulation dot1q

no ip address

On the C6509

interface GigabitEthernet9/1

description Caboto_1GB_Link

switchport

switchport trunk encapsulation dot1q

switchport mode trunk

no ip address

udld port

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: GigabitEthernet Trunk config

Hi Friend,

By default the switchport is in dynamic desirable mode which means it will attempt to form a trunk if the neighbor port is already a trunk port.

Your cat6k is already configured for switchport mode trunk so the 3550 is working in dynamic desirable mode and is the reason it is forming a trunk without that command but there is no harm in giving this command on 3550 also to unconditionally make it a trunk port.

HTH, please rate post

Ankur

5 REPLIES
Cisco Employee

Re: GigabitEthernet Trunk config

Hi Friend,

Its really not required. You can configure first "switchport mode trunk" on your 3550 interface and also remove "switchport access vlan 100 " from that interface.

no switchport access vlan 100

swithport mode trunk

HTH

Ankur

*pls rate all helpfull post

New Member

Re: GigabitEthernet Trunk config

Thanks you very much. I have just gone unto the switch and it has as description

trunk Set trunking mode to TRUNK unconditionally

Why do I really need to do this as it is working as trunk without this statement

swithport mode trunk

Thanks

Cisco Employee

Re: GigabitEthernet Trunk config

Hi Friend,

By default the switchport is in dynamic desirable mode which means it will attempt to form a trunk if the neighbor port is already a trunk port.

Your cat6k is already configured for switchport mode trunk so the 3550 is working in dynamic desirable mode and is the reason it is forming a trunk without that command but there is no harm in giving this command on 3550 also to unconditionally make it a trunk port.

HTH, please rate post

Ankur

New Member

Re: GigabitEthernet Trunk config

Get rid of :switchport access vlan 100

It is a trunk VLAN 100 will be is allowed because it is a trunk. On the C3550 you will need to put : switchport mode trunk

The 6509 is set based switch, the out put you have for the 6509 does not look right????

Cisco Employee

Re: GigabitEthernet Trunk config

Hi Gpartch,

6509 can also work into IOS mode which is known as Native mode. May be the one which you are having must be running CATOS which is hybrid mode.

HTH

Ankur

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