Ethernet Switches & Routers

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Contributor
Posts: 46
Registered: ‎11-01-2010

"No dual-mode" on uplink lose connectivity to vlan

I have misconfigured one of my uplink port as dua-mode for vlan 1. I want to change that and configure the port as Tag for vlan 1
That Uplink is connecting a Brocade Layer 3 switch to a Cisco Layer 3 switch
But when I "no dua-mode" on this port, I lose connectivity to that vlan on that switch to the other switch. But the port is correctly tagged between my 2 switchs.
I use Dual-Mode on my other ports that I have phones and computers conencted to, but I dont need a dual-mode on an uplink port.
BEFORE removing Dual-mode
PORT-VLAN 1, Name LEGACY, Priority level0, Spanning tree Off
Untagged Ports: (S1)   2   3   4   5   6   7   8   9  10  11  12  13
Untagged Ports: (S9)   4
   Tagged Ports: (S1)   1
   Tagged Ports: (S3)   1
   Tagged Ports: (S4)  19  20  21  22  23  24
   Tagged Ports: (S9)   5
   Uplink Ports: None
DualMode Ports: (S9)   3
AFTER
PORT-VLAN 1, Name LEGACY, Priority level0, Spanning tree Off
Untagged Ports: (S1)   2   3   4   5   6   7   8   9  10  11  12  13
Untagged Ports: (S9)   4
   Tagged Ports: (S1)   1
   Tagged Ports: (S3)   1
   Tagged Ports: (S4)  19  20  21  22  23  24
   Tagged Ports: (S9)   3   5
   Uplink Ports: None
DualMode Ports: None
Config on Brocade:
!
interface ethernet 9/3
port-name "Uplink Catalyst Geloso Laval"
dual-mode  1
ip rip v2-only
ip rip learn-default
!
vlan 1 name LEGACY by port
tagged ethe 9/3
!
Config on Cisco switch
interface FastEthernet0/6
description "BROCADE Backbone"
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,10
switchport mode trunk

Thanks for your help!

Contributor
Posts: 50
Registered: ‎01-07-2011

Re: "No dual-mode" on uplink lose connectivity to vlan

A Cisco switch will send the default-vlan as untagged. So when connecting to a Cisco switch, you will in most cases have to use the dual-mode command.

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