[cisco-nas] Routing - centralized address pool - multiple NAS

[Pierre de La Motte]

Hello,
I would like to implement a configuration where a single address pool is 
hared among multiple NASes (LNS as a matter of fact).
The address pool is shared among NAS through a Radius server.
A basic way to do it would be to split the address range associated with 
the pool into several address sub-ranges, each of them allocated to a 
specific NAS. On receiving an Auth Req Radius would just return the IP 
pool identifier and each NAS would allocate an IP address locally 
associated with the IP pool identifier.

Now, I would like to allocate susbcribers IP addresses directly from 
radius from a global address range shared among the NAS.

I have two questions with regard to such a configuration - routing and 
session control:
- what is the best way to implement such a scheme from routing point of 
view. How the downstream router will route the subscriber returning 
traffic to the right NAS, knowing that an address may be allocated to 
one NAS then to another over a period of time.
- how to avoid session duplication over the NAS group - two subscribers 
using the same username, resulting in having two active sessions active 
terminating on two different NASes.

Thank you
-Pierre

-- 
Pierre de La Motte
pierredelamotte at yahoo.com