Networking Blog

A brief tutorial how to configure dot.1q ( tagged vlan ) Layer3 interface on Cisco 1800 series. ( on WAN interface ). First will create vlan 777 in vlan database

cisco1800#vlan database
cisco1800(vlan)vlan 777
VLAN 777 added:
    Name: VLAN0777
cisco1800(vlan)#
cisco1800(vlan)#vlan 777 name dot1q_vlan_on_WAN_interface
VLAN 777 modified:
    Name: dot1q_vlan_on_WAN_interface

Now verify vlan:

cisco1800#show vlan-switch

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa4
2    Servers                          active    Fa1, Fa2
3    SERVICE                          active    Fa3
5    VLAN0005                         active
99   VLAN0099                         active
777  dot1q_vlan_on_WAN_interface      active
1002 fddi-default                     active
1003 token-ring-default               active
1004 fddinet-default                  active
1005 trnet-default                    active

The last step is to create the tagged subinterface on FastEthernet0:

cisco1800(config)#interface FastEthernet 0.777

After the interface number just enter “.” (dot ) and vlan id.

cisco1800(config-subif)#encapsulation dot1Q 777
cisco1800(config-subif)#ip address xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx

View configuration:

cisco1800#sh ru interface FastEthernet 0.777
interface FastEthernet0.777
 encapsulation dot1Q 100
 ip address xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx
 no snmp trap link-status