[j-nsp] RE - 6. vlan-id 0 (Bit Gossip)

[sthaug at nethelp.no]

> do you know what is the meaning of vlan-id 0?
> According to: http://en.wikipedia.org/wiki/IEEE_802.1Q
> "VLAN Identifier (VID): a 12-bit field specifying the VLAN to which the
> frame belongs. A value of 0 means that the frame doesn't belong to any
> VLAN; in this case the 802.1Q tag specifies only a priority and is
> referred to as a priority tag"
> 
> How would I match this Juniper config:
> 
> show configuration interfaces ge-0/0/0
> vlan-tagging;
> unit 0 {
>     vlan-id 0;
>     family inet {
>         address 1.1.1.1/30;
>     }
> }

Is your goal to be able to handle untagged traffic on this link? With
IQ2 PICs (or GigE ports on an MX) you can handle both untagged, single
tagged and dual tagged Ethernet frames on the same link. Forget about
VLAN id 0, the relevant question here is untagged or not.

> on a cisco device on the other end of the cable where vlan starts from
> 1?
> 
> Instead of configuring a subinterface configure ip under the main
> interface:
> 
> //r2(config-subif)#encapsulation dot1Q ?
>   <1-4094>  IEEE 802.1Q VLAN ID required
> 
>  r2(config-if)#ip address a.a.a.a m.m.m.m
>   <1-4094>  IEEE 802.1Q VLAN ID required

Here is a working example of a Juniper configuration which generates
untagged frames for VLAN 120 (and only for VLAN 120). All other VLANs
will be tagged.

ge-0/2/0 {
    flexible-vlan-tagging;
    native-vlan-id 120;
    unit 120 {
        vlan-id 120;
        family inet {
            address 172.16.120.202/24;
        }
    }
}

Documented at for instance

http://www.juniper.net/techpubs/software/junos/junos93/swconfig-network-interfaces/configuring-mixed-tagging-support-for-untagged-packets.html#id-12185086

Steinar Haug, Nethelp consulting, sthaug at nethelp.no