I have c1721 router at a customer premises. IOS version is c1700-k9sy-mz.122-32.bin.
ISDN backup is not working automagically. isdn test call from the router(1721) works. dropping the backup statement on the interface(1721) works but if you SHUT the interface on the gateway router they connect to on our side, the ISDN does not come up.
It cannot be IOS on the gateway, as all other backups work fine except for this one.
It is standard behavior for IOS (and always has been) for the backup interface command that it will initiate the backup only when there is a problem. Issuing the shutdown command is not a problem. The IOS assumes that if you issue the shutdown command that you meant it to be down and therefore will not initiate the backup interface. The interface must go down or the line protocol of the interface must go down for the backup interface to become active.
This document gives several answers on frequently asked questions for PFRv3 channel state behavior.
Q1: What are all the channel operational states from a BR (border role) perspective and what are the rules/conditions to be in each st...
The need was to reach an host inside a LAN through a VPN connection managed by the LAN gateway (Cisco 1921).
The LAN gateway performs NAT and there was a dedicate nat rule for the host i wanted to reach through VPN.
I couldn't connect to the hos...