[j-nsp] VLAN range support on MPLS based L2VPN?

[sthaug at nethelp.no]

> 1) Encapsulation extended-vlan-ccc is only for the purpose of using extended
> VLANs (or large number of VLANs) OR there are other differences as well?

You can't have IP subinterfaces with extended-vlan-ccc.

> 2) What is the valid VLAN IDs range when using extended-vlan-ccc encap?
> There are contradictions on Juniper online doc. At one place they are saying
> "For the extended-vlan-ccc encapsulation type, VLAN IDs from 0 through 1023
> are valid, allowing you to make up to 1024 VLANs for the CCC connection."
> And on other place "For extended VLAN CCC encapsulation, all VLAN IDs from 1
> through 4094 are valid. VLAN ID 0 is reserved for tagging the priority of
> frames."
> On practice, i can only use b/w 1 to 1023 IDs.

Note that there are also PIC specific hardware limits - for instance
the 4 port FE PIC for M7i/M10i restricts you to VLAN IDs up to 1023.

I believe that with a modern PIC (e.g. SFP-based GigE for M7i/M10i),
you should be able to used a wider range with extended-vlan-ccc. But
if you have the SFP based GigE PICs (both standard and IQ) you can
also use flexible-ethernet-encapsulation which lets you have the 
best of both worlds - a wide VLAN range *and* mixing of L2 and IP
subinterfaces.

> 3) What is the usual practice of providers while using L2VPN, will this
> small range of VLAN Ids enough for them? OR there are other techniques?

We use VLAN stacking heavily (outer and inner VLAN tags), typically we
choose the outer tag and the customer chooses the inner tag. You need
IQ PICs to handle outer/inner though.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no