[cisco-voip] SRST Significant Digits?

[Adam]

I have a site where the telco is sending seven digit dnis for inbound
calls. The phones only have four digit extensions, so the MGCP
configuration on the gateway is set for four significant digits and
everything works fine. The problem is when the link goes down and
things fail over to SRST. The phones register to the gateway just fine
with the four digit DN, but now the calls don't match and get routed.
Is there some way to set SRST to only look at four digits on incoming
calls?

Thanks,
Adam