January 1, 2008

Enable ISN dialing on your Linksys IP Phone

Finally I have set up an ISN support on our Sip Express Router @ CNL. After I tried to make my first ISN call to the 1234*256 test number (screaming monkeys :)) from my Linksys SPA962 IP Phone I was a bit disappointed :-( To my big surprise after pressing the dial button, it showed just an "Call ended" message without any additional information. It was weird that it doesn't even showed the called number what it normally does. From my experience, the best thing do in these situation is to turn on some kind of debug on SIP Proxy server or if available on IP phone. I used my favorite "debugger" tool on SER server: ngrep. Dialing from my IP Phone once again, but got nothing. No SIP INVITE messages from my IP phone at all. After further investigation, I found the problem: the default dial plan used in Linksys IP phones does not support the star character "*" in a dialed number: (*xx|[3469]11|0|00|[2-9]xxxxxx|1xxx[2-9]xxxxxxS0|xxxxxxxxxxxx.) To enable ISN dialing you must add this dial pattern: x.*x. After adding the ISN dial pattern, your dial plan may look like this: (*xx|[3469]11|0|00|[2-9]xxxxxx|1xxx[2-9]xxxxxxS0|xxxxxxxxxxxx.|x.*x.) If you are using some prefix for outbound dialing, like 7*....... and want to use it for ISN calls as well, then you must add a pattern like "7*x.*x.". My dialplan now looks like this: ([1-7]xxxS0|0x.|x.*x.|7*x.*x.) Lines 1xxx - 7xxx are our internal lines, 0x. are outgoing trunks, x.*x. is an ISN pattern as well as 7*x.*x.