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qsig and call forwarding

Hi I am having a problem with forwarding a phone to voice mail over leased line.I have 2 2600's each with qsig connection to pbx.when a phone is forwarded over the leased line from one end to the other it only works 50% of the time ie. when it doesn't work it seems the phone just rings out and never goes to voicemail.I have looked at q931 debugs and for a good and bad call both debugs look identical.Also when there is success I notice that more than 1 isdn channel is being brought up.For it to work it seems to need 4 channels which seems crazy.My signaling config is as follows.interface Serial1/0:15

no ip address

no logging event link-status

isdn switch-type primary-qsig

isdn protocol-emulate network

isdn incoming-voice voice

isdn bchan-number-order ascending

fair-queue 64 256 0

no cdp enable

is there any tweeking I can do to rectify this situation or is there an inherant problem with the amount of channels being seen as busy by the pbx for a successful forwarding to voicemail?Another thing is that it works every time when calling the ddi number which is forwarded over leased line to voicemail.Any opinions appreciated thanks!


Re: qsig and call forwarding


This happens because call manager does not support route optimisation.

Site a has extension 3000 and voice mail on 4000. There is a route to site b sending anything begining with 2XXX.

Site B has extension 2000, call forwarded to 4000. and a route to site a for 4XXX

Ext 3000 calls 2000 this opens up 1 channel accross the link, 2000 then forwards the call to 4000, opening a second channel accross the link. When the voice mail answers the call there are now 2 channels active. Call Manager can not tell the other PBX that it's the same call due to lack of Route optimisation. (or Anti-Tromboning).

This explains 2 channels, Why you have 4 I can't understand, unless there is a loop being formed, but this would show up as ALL channels becoming busy very quickly and then returning engaged. It may be message notification from the VM server calling the phone and being bounced back to itsself.

Have a look at the routing at both ends, make sure there aren't any digits being added or stripped on both the inbound and outbound gateways.

The calls coming in on ddi and over the leased line don't take up multiple channels as the call only passes once over the link (direct to VM).

Not a complete answer but hopefully gives some pointers.


New Member

Re: qsig and call forwarding

Paul thanks for your input.I suppose I should have mentioned but I'm not using call manager.Still no more than 2 channels should come up so I'm still in the dark regarding that.Calls coming in on the ddi go over the link twice because they are routed over the link from the pri in the central site if you get me.So it's the same scenario just a different entry point.

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