ISDN PRI line uses for both remote access and dial backup

[dnguyen]

Can someone tell me if this is possible. I need to have remote access for about 12 users via dialup, at the same time I would like to implement ISDN dial backup for the WAN of 10 sites. Can I use one single PRI to serve both purposes? the site with the PRI will have 12 channels for remote users and the other channels will be used as ISDN backup to initiate the calls to the remote routers. If you have a sample config would be grateful.

Thanks

[makchitale]

Yes, that is possible...the PRI has 23 B channels. 12 will be used for dialup users & the remaining for ISDN backup.

Now assuming that we will not need all the backup at a given time, we can actually configure multilink for the backup.

http://www.cisco.com/en/US/customer/products/hw/univgate/ps505/products_configuration_example09186a0080094a49.shtml

In the above config can add the backup configs: (look for backup keyword)

http://www.cisco.com/pcgi-bin/Support/browse/psp_view.pl?p=Internetworking:ISDN&viewall=true

Thanks, Mak.

[dnguyen]

Thank you Mak. for your quick response. Can I do the same with a Cisco 3620 series router with a one-port channelized T1/ISDN-PRI Network Module (NM-1CT1-CSU) and a 24 port Digital Modem Network Module (NM-24DM)? and have Async dial in for users and ISDN dialout to remote routers on the same PRI?

Thank you again.

[makchitale]

Sure, basically the config will remain the same except for the line number & interface number based on the slot where the NM is inserted.

Thanks, Mak.

[vcjones]

Supporting both dialin and dialout, both ISDN and analog, on the same PRI (or BRI, for that matter) works fine. Just use dialer profiles rather than legacy dialer maps. However, be aware that there is one potential significant limitation. The commands available to limit or reserve some number of channels assigned to a particular dialer pool are only applied to dial out dialers. If you cannot control the number of incoming calls, you could find yourself in the position where you need to place an outbound call and there is no free "line" available.

You can limit the number of incoming users by appropriate configuration of your RADIUS or TACACS server, but that does not prevent excess incoming calls from tying up a channel while they are being rejected.

Good luck and have fun!

Vincent C Jones

www.networkingunlimited.com