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Crossed calls using E&M trunks

Using two 3660s with eight E&M ports each. These eight trunks being used for

IP connectivity over WAN. 'connection trunk' command is used to map

for example 'Port 1/0/0' on router A to 'port 1/0/0' on router B.

The problem is that sometimes voice calls get crossed and sometimes

a person accessing the trunk from site A gets unintentionally connected to

someone calling from Site B.


Re: Crossed calls using E&M trunks

Is it possible to change the hunt order on the pbx? Site A starts with port 1 and goes up, Site B starts with port 8 and goes down. This would help minimize the problem.


Re: Crossed calls using E&M trunks

First of all thanks for the reply.

The PBX is the Alcatel 4400. According to the people configuring it they could not do it (I had already suggested this option to them). They have a sequentilal hunting sequence and either they don't know how to change the sequence or the product does not support it.

Initially I was not using the 'connection' command on the voice ports. The router was routing the call based on the digits received from the PBX. After the problem in question started occuring, I used the 'connection plar' and then the 'connection runk' command. This has drastically reduced the occurrence of the problem but has not completely alleviated it.

Re: Crossed calls using E&M trunks

If the Alcatel guys can't re-configure the hunt group for you in programming then you can change it yourself physicaly, just unplug the connections on one of the routers and plug them back in the starting from the opposite end. That way you have created the crossover and if glare is a problem then this should help.

I suspect that the problem you have is a little more basic. The idea behind E&M is that glare shouldn't happen at all due to the off/on-hook signalling, you probably will find that the trunks are either oversubscribed or your signalling set-up with the 4400 is incorrect (you are set to delay start and they are wink etc.). Try dropping the number of trunks down to a single link and test simultaneous calls from both ends and use an AV meter to check the signalling wires, it may be that either the router or the 4400 are ignoring them.



Re: Crossed calls using E&M trunks

Thanks for the reply.

For he first part:

The hunting sequence on the PBX is such that the PBX will seize port 1/0/0,

then 1/0/1 even if 1/0/0 is not busy. Therefore it would seem that attaching the wires the other way around would not solve that problem as what we actually want the PBX to do is to seize the same trunk again and again until it becomes busy (and this is something that can't be changed at least for now).

For the second part:

The router is configured with immediate start signaling (as this is what the PBX people have said is configured on the PBX). Do you thnik that chaning the signaling type will help? We have tested the voltages on the signaling wires and they are ok (also verified using debug and show commands)

Re: Crossed calls using E&M trunks

First part,

Fair point if the hunt group is Cyclic then there's nothing that can be done. It still may be worth doing though, because one end will be going 1-2-3-4-5-6-7-8, and the other end 8-7-6-5-4-3-2-1 so they are less likely to get in sync and repeatedly glare.

Second part,

This might be the problem, because it's using immediate start there is no way for the PBX to check if the line is in use before starting to send digits, so if a call is in-coming just end up with collision. Try setting both sets of equipment to wink start or delay dial, at least this means it will check before sending.


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