[c-nsp] MPLS Design doubt

[Annu Roopa]

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 ?
 
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 ? 
 
Any ideas ? Anyone who has implemented or has config examples ?
 
Thanks for your answers.
 
Annu
 
 

		
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