[c-nsp] MPLS Design doubt

[Oliver Boehmer (oboehmer)]

Annu Roopa <> wrote on Friday, September 09, 2005 5:18 PM:

> Hi Folks,
> 
> I am in the process of migrating a ISP customer with IP-core, who has
> ISDN and VPDN for few of their customer sites to a network where the
> core would be MPLS. Wanted to clarify some doubts and see what others
> may have done or have to say.   
> 
> 1. The ISP is using ISDN as backup to existing leased lines. They are
> currently using the same IP address/subnet for ISDN as the leased
> line (being allocated through the RAS box).  
> 
> With MPLS this can be done using "ISDN backup in MPLS core",but is it
> possible to use the same IP subnet for ISDN when in MPLS.  Any links
> or docs discussing this ?  

"ISDN backup in MPLS core" is a feature allowing the backup of an
MPLS-core link (i.e. PE-P or P-P) via ISDN (usually seen in smaller
Enterprise MPLS deployments).

I guess you want to backup an PE-CE (i.e. vrf) interface, what you need
to look at is the "Remote Access to MPLS VPN" where Dial connections can
terminate into the VRF. There are basically two solutions:

- direct dial-in into a PE with ISDN interfaces (only limited platform
support, i.e. 36xx and 72xx)
- dial-in into any access server and L2TP tunnel into an LNS-PE where
the virtual-access interfaces terminate in the customer VRF.

With both solutions, you can set up static routes (I recommend to do
this via Radius).

> 
> 2. There are some existing VPDN customers for this ISP who do L2TP
> from their remote sites to the central site. 
> 
> When migrating over MPLS would VPDN over MPLS be still possible ? Did
> find docs saying it can be done - but did NOT find any doc showing
> the configs or example. Would it be a better to do VPDN over MPLS
> (assuming it can be done ) or PPPoMPLS ?   

You can use the L2TP solution for this case as well.

Search CCO for "Remote Access to MPLS VPN" to find more information
about this.

	oli