[cisco-bba] Specifying metric/cost for primary/backup dialin users on LNS

[Johannes Jakob]

Dear collegues,

I'm having problems implementing a new LNS setup.

For load balancing and redundancy reasons, we've got several LNSes (cisco 7200 platform) to terminate xDSL dialins.
The CPEs, that are connecting via xDSL, do have two dialins configured. One for primary usage, one for backup.
On both these dialins (different user credentials), they are assigned the *same* IP-Address, but they are setting local routes that prefer the primary connection via local metric - no routing protocols applied.

Some of these CPEs do have subnets routed to them via radius AVPair, some don't.


On the CPE side, everything is working fine, but now I have to implement the ISP side of this setup.
The LNSs on our side talk OSPF with each other and with the backbone. DialedIn CPEs (their IP-addresses) are being redistributed via ospf to the backbone (for speed reasons, so that the fallback to the backup line is instant).

Because of the setup (round robin, sgbp and mmp) there are two cases to consider.
a) primary and backup dialin are terminated on the same LNS (1 OR 2)
b) on different LNSs (1 AND 2)

My problem now is: How can I set local metrics for the dialin CPE IP-Address and not only to the framed-routes that are routed via this address, and how can I change the OSPF cost of the routes the LNS is redistributing on client connect, so the LNS locally knows which link is the primary and which the backup one AND the backbone knows, on which LNS it can find the primary and on which the backup link so that both cases are perfectly taken care of?

I tried to illustrate my problem with this diagram: http://dl.dropbox.com/u/114378/metric-problem.pdf

The LNSs are running
Cisco IOS Software, 7200 Software (C7200-A3JK9S-M), Version 12.4(25b), RELEASE SOFTWARE (fc1)



Any help would be appreciated, I'm rather desperate to find an appropriate solution for this problem....

Thanks in advance,

 John

P.S: show ip route on the LNS in case 2:
C      1.1.1.1/32 is directly connected, Virtual-Access4
                          is directly connected, Virtual-Access3

and on any other ospf enabled box in this vlan the ospf routes are received with the same default cost and not with the one I specified for the link via avpair.