Subinterfaces on cisco 3900 router

[Brian McNair]

I have a cisco 3900 Series router and I need assistance in configuring sub-interfaces under G0/0 interface. This issue I have is when I used g0/0.1 and ecap dot1q 10 native this is the only vlan 10 is the only vlan that works. Do I have to put the native vlan command under the g0/0 interface? if so can you show me the command to get this to work.

The router is connected to a Cisco 2960 with a 802.1q trunk configuration to support vlan 10,20,21.

[Jon Marshall]

You only use the "native" keyword on the subinterface for the vlan that is the native vlan on the switch trunk port.

So a "sh int trunk" on the switch should tell you the native vlan.

Each vlan needs a subinterface on the router.

Jon

[Brian McNair]

Jon,

below is what I have configured on the router

int g0/0

no ip add

int g0/0.1

ip add 10.0.0.1

encap dot1q 10 native

int g0/0.2

encap dot1q 20

ip add 20.10.0.1

int g0/0.3

encap dot1q 30

ip add 20.22.0.1

Switch

in g0/1

switchport trunk nat vlan 10

switchport trunk allowed vlan 10,20,30

switchport mode trunk

With the configuration I can only ping devices in vlan 10

[Jon Marshall]

The basic configuration looks fine.

When you say you can only ping devices in vlan 10 do you mean from the router ?

Couple of things to check -

1) the clients in each vlan have the corresponding subinterface IP address as their default gateway

2) the client ports on the switch are allocated into the correct vlans

Jon

[Brian McNair]

I'm checking my configuration and will let you know

[Brian McNair]

Jon it was my configurations I forgot to add the ip address on the router side everything worked as you stated. Thanks