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New Member

Trunk ports on a VLAN

Folks,

I have a 2 switches, a cat4006 & a 3548XL. I have added an additional vlan, vlan3, on both switches and set up a vtp domain, MYDomain, on the 4006 which is in server mode.

The 4006 can see the MAC addresses of those machine on its port but the 3500 is seeing nothing even though a show vlan is showing the port assigned as active.

my question:

do i need to set a trunk port between the 2 switches, they're linked by the gigabit port on the 3500 to the 4006.

If this is the case can i do this without disrupting traffic from the default vlan, i.e will all traffic still be switched over the trunk port

thanks for your help in advance

1 ACCEPTED SOLUTION

Accepted Solutions

Re: Trunk ports on a VLAN

Hi,

my understanding is there is no trunk between 4006 and 3548 yet?

You've got two possibilities then:

a) Add a new connecting line (access ports assigned to VLAN3 on both ends) between 4006 and 3548. But I don't think you'd do this.

b) Configure trunk on the current line.

Use "switchport mode trunk" command on 3548 IOS. You also need to decide which trunk encapsulation to use. The command is "switchport trunk encapsulation dot1q|ISL" on IOS. Depending on IOS or CatOS running on 4006 you need to configure the other side of the trunk line (CatOS commands is "set trunk mod/port nonegotiate dot1q ....").

Be carefull, the line goes down/up while enabling trunking on it.

Also check the VTP configuration. You need the same VTP domain name, password (if used. Determine who's VTP server or client. Check VTP config revision numbers - the hihgest number wins, i.e. if your 3548 is a client but it's revision number is higher then the server's one, it will overwrite the server config! (The safest way is to clear the revision number to zero - change the VTP domain on the client to "something-else" and then back to MYDomain - it will clear the revision number.)

Good luck,

Milan

2 REPLIES

Re: Trunk ports on a VLAN

Hi,

my understanding is there is no trunk between 4006 and 3548 yet?

You've got two possibilities then:

a) Add a new connecting line (access ports assigned to VLAN3 on both ends) between 4006 and 3548. But I don't think you'd do this.

b) Configure trunk on the current line.

Use "switchport mode trunk" command on 3548 IOS. You also need to decide which trunk encapsulation to use. The command is "switchport trunk encapsulation dot1q|ISL" on IOS. Depending on IOS or CatOS running on 4006 you need to configure the other side of the trunk line (CatOS commands is "set trunk mod/port nonegotiate dot1q ....").

Be carefull, the line goes down/up while enabling trunking on it.

Also check the VTP configuration. You need the same VTP domain name, password (if used. Determine who's VTP server or client. Check VTP config revision numbers - the hihgest number wins, i.e. if your 3548 is a client but it's revision number is higher then the server's one, it will overwrite the server config! (The safest way is to clear the revision number to zero - change the VTP domain on the client to "something-else" and then back to MYDomain - it will clear the revision number.)

Good luck,

Milan

New Member

Re: Trunk ports on a VLAN

Milan,

Thanks for such a detailed response

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