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New Member

Fax Problems

Hi

I am experiencing Fax problems in my Cisco Voice network.There are about different problems for each fax machine.

All the fax machines are the same model.

1. Faxes unable to send out to external lines

Faxes call an outside line, when the remote fax connects, after a minute of negotiation, the call drops, fax says 'Communication Error'

2. Faxes send mulitple copies of the first page

Faxes call an outside line, when the remote fax connects, but then the fax thinks the call has failed, but has sent the first page. It then tries to resend with the first page being resent again and again.

This has been affecting the faxes on the VG224.

If you need to any information to find a solution please reply me back.

Thanks

Vino

15 REPLIES

Re: Fax Problems

A common problem with faxes is that they are very susceptible to poor line clocking, latency can also be a factor.

Verify your clock source on your outgoing PSTN gateway and ensure that there are no line slips or errors on the controller which is your primary network-clock.

If there are errors, try choosing an alternate controller for your network clock-soure if available.

Rgds

Allan.

New Member

Re: Fax Problems

Hi allan

There are like 20000 Slip secs in past 24 hrs in the controller and the clock source is line. I am not sure about the network clock-source and whether it is to be applied to exisiting controller. I have another gateway that doesn't have these errors but not sure how about changing the faxes to the gateway.

Please advise

Thanks

Vino

Re: Fax Problems

These line slips that you are referring to, are these present on the controller for your outbound PSTN breakout?

If this is the case, then this could be the source for your fax training and communication errors.

Within your configuration you should have configured your E1 or T1 with network-clock-participate and select, something like as follows:-

network-clock-participate wic 2

network-clock-select 1 E1 0/2/0

If you have another E1 or T1 on the same gateway, and no slip or errors are evident on it, then I would recommend changing the clock-select like as follows:-

no network-clock-select 1 E1 0/2/0

network-clock-select 1 E1 0/2/1

This would help to isolate whether the slips are the cause behind your fax problems.

Please post your PSTN gateway config for review.

Rgds

Allan.

New Member

Re: Fax Problems

Hi Allan

Many thanks for your comments... Ys these slips are occurring in the controller on the outbound PSTN breakout...

I can change the network-clock-select to the e1 channel that had slip errors. But is this going to affect anything on my live network or going to cause any problems ?

Thanks

Vino

New Member

Re: Fax Problems

Also Allan

I have a gateway in another site with the same configuration as this one but the major difference is only one E1 is up and the other e1 is down the working one .

and also no network-clock-participate is configured and clock source line in both the working and non-working gateways.

I cannot see the network-clock-select command in both of them..

Re: Fax Problems

The clock source configured as line on both the MGCP gateways is correct, it is only which line the clocking is derived from that requires changing.

I would recommend that you configure both the network-clock-participate and select at a time which is convenient to your business.

You can never offer assurances to the severity of the impact in-hours, therefore depending on the severity of the fax issue can the business afford disruption during hours in order to isolate the problem. I fear not.

In the meantime I would escalate the issue of line slips to your carrier, providing of course you can be certain that these are not attributed to the E1 cabling between their equipment and yours?

Rgds

Allan.

New Member

Re: Fax Problems

Also Allan

I have a gateway in another site with the same configuration as this one but the major difference is only one E1 is up and the other e1 is down the working one .

and also no network-clock-participate is configured and clock source line in both the working and non-working gateways.

I cannot see the network-clock-select command in both of them..

Re: Fax Problems

I would recommend configuring the network-clock-participate and select commands out-of-hours on both your gateways for each appropriate E1 connection. Providing of course that there are no slips present on that interface and take it from there.

Rgds

Allan.

New Member

Re: Fax Problems

Allan

I would carry out the change and will inform you of the result... Many thanks for your help ...

Vino

New Member

Re: Fax Problems

Allan, thanks for your post. I have discovered on all of the CME routers I have deployed do not have the network-clock-select command and on every single one I am getting tons of SLIP errors.

I understand the need for this command but it makes me wonder what would happen if you had a VWIC T1/E1 and a WIC2-T1 CSU in the same router. Which card should have the higher priority for clocking? What if your Voice PRI and your Data T1 are from different carriers?

Thanks,

Chris

Re: Fax Problems

To allow the ports on the specified network module for Voice or WAN interface card to use the network clock for timing, you need to use the network-clock-participate command as mentioned previously.

However, each port can be selected as the clock source with the network-clock-source command.

This configures the appropriate interface to supply clock to other ports or network modules that you have chosen to participate in network clocking with the network-clock-participate command.

For example, say you have configured a vwic2-2mft-e1-t1 as follows:-

network-clock-participate wic 2

network-clock-select 1 E1 0/2/0

This synchronises the clocks for both port on the dual e1/t1 from 0/2/0.

Therefore if you have a separate vwic and wic in the same router, then do not specify one or the other with network-clock-participate.

This will essentially exclude it from synchronising the port. The port would then resort to using the clocking method stipulated under the controller, normally either line or internal.

Hope this clarifies the situation.

HTH

Allan.

New Member

Re: Fax Problems

Hi Allan,

I have connected the fax device on the FXS port and we are able to send faxes. But when someone tries to send us a fax, the phone keeps ringing but the fax doesn't start and we are not able to receive faxes. I am sending you the configuration can you please assist me on this.

Silver

Re: Fax Problems

Hi,

I've had loads of problems with faxes in the past, some of them due to people switching to different fax models (brands).

What's the baud rate, have you set this to the minimum (9600) and tested. Have you tried changing a few of the fax settings?

New Member

Re: Fax Problems

Hi Tim

Basically all the fax are same models and configured similarly. I haven't tested using the baud rate 9600, which I will do.

I can see mgcp fax t38 inhibit command in our VG,which as far as i read was to deny usage of mgcp based t38 on gateway. I am not sure whether it is related to the problem.

Thanks

New Member

Re: Fax Problems

"2. Faxes send mulitple copies of the first page

Faxes call an outside line, when the remote fax connects, but then the fax thinks the call has failed, but has sent the first page. It then tries to resend with the first page being resent again and again.

This has been affecting the faxes on the VG224."

Im also seeing this with the VG224 and UC 6.1.

Ive check the controller and there are no errors. Has anyone seen this issue where there are no ISDN issues?

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