I have not been able to find a definitive solution to this query anywhere. Can a 1750 failover on it's own interfaces? Ie - ISDN or Serial link to ISP on Interface A and ADSL Link to ISP on Interface B. If the default ISDN link goes down can the ADSL Link come up automatically [could be to a different ISP or the same]?
I know you can have failover between two routers with HSRP. But can you do the above?
Failover with ISDN is always problematic, since the ISDN interface will ALWAYS be up/up (spoofing). So failure of ISDN (layer1 or layer 2) will not effect the dialing. What you would ordinarily do, with multiple ISDN interfaces, is to put them into a rotary group and use the command "dialer rotor best" so that we will rollover to the next interface when dialing fails, and we will automatically try the last successful interface for dialing. In your case, however, the other interface is ADSL, and I don't know of a way to incorporate this.
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