Connection a Fax Machine to FXO/FXS Ports to Provide Dial-tone?

[Matthew Martin]

Hello All,

Router: ISR4321

Inventory:
NAME: "NIM subslot 0/2", DESCR: "NIM-2FXS/4FXO Voice Analog Module" PID: NIM-2FXS/4FXO , VID: V01, SN: XXXXXXXXXXX

One of our branch locations is getting their telephone numbers ported from their local carrier to our HQ's SIP Trunk, and then we will route their calls to them via CUCM over our MPLS.

Now, I've done this a few times with Fax Machines where I spliced a Ethernet cable so one end is a telephone plug and the other stays as RJ-45. This way The Fax machine can connect to an Ethernet wall-port. But, I know this location has a few extra FXS (*and possibly FXO ports as well), and was wondering if there is a way to connect a fax machine to an FXS port and be able to route a call/fax to a fax machine connected to an FXS port...?

I've never tried connecting anything other the incoming POTs lines to FXO ports before, so I wasn't sure if anything like this was possible...

Any thoughts or suggestions would be greatly appreciated!

Thanks in Advance,
Matt

[Chris Deren]

Absolutely, that is what FXS ports are for, ability to connect analog stations such as faxes to your voip infrastructure. You just need to make sure you configure the voice GW servicing the FXS port either as SIP/H323/MGCP (SCCP is not recommended for faxing over SIP trunk as it does not support protocol-based T38), and configure properly CUCM, i.e. trunk/RG/RL/Route pattern if using SIP or GW and port if using MGCP.

[Matthew Martin]

Hi Chris, thanks for the reply and sorry for the delay responding. I ended up needing to start work on  another project and haven't gotten back to this since. Plus, we're still waiting for the number to be ported from the current local TelCo (*regular POTs line) at this remote location, to our SIP/VoIP provider for our Main-HQ location.

Currently the ISR4321 is configured as an H.323 Voice Gateway in CUCM. I know about the t38 commands in the "voice service voip" section in the config. But, is that only for the SIP configuration, correct? Like this below:

voice service voip
 fax protocol t38 version 0 ls-redundancy 0 hs-redundancy 0 fallback pass-through g711ulaw

Can t.38 be configured on an H.323 Gateway, or is it for SIP only..?

Also, what would be a good base configuration for the FXS port? Would you be able to provide a sample FXS port configuration?

Thanks again for the reply, very much appreciated!

Thanks,
Matt

[Matthew Martin]

One other thing...

So after the phone number porting is complete the call will start coming in through our SIP Trunk at our HQ. The SIP CUBE will then send the call to CUCM. Now, on CUCM I created a Route Pattern that will match the entire incoming called number, and CUCM will then pass the call on to the Route List that is configured for the Remote location's Voice Gateway --> "<ip-addr> (All Ports)".

Now, on the remote location's ISR4321 I was checking out what can be configured on the FXS ports and I don't see anything that can be configured to tell the incoming call to send the call to that specific FXS port. The FXS ports don't seem to have anything like the "incoming called number", "destination-pattern", etc... So I'm wondering how it will know where to send the call, or in this case where to send the Fax.

I know on our 2821s in our HQ, which are configured in CUCM as 2821 devices, you can actually see all the "Endpoints" (*which are the individual analog ports) of this 2821 gateway. So I was wondering if I needed to do something like that, where I tell CUCM exactly what port on the Voice Gateway to send the call to.? But, I guess on the H.323 Gateways you can only really specify (All Ports) in the Route List. So I wasn't sure what exactly I need to do for that...

Does that make sense?

Thanks Again,
Matt

[Chris Deren · Accepted solution]

If the ISR4321 is controlled via H323 or SIP then you require proper dial-peers on the GW to point the call to the port. You will need to add inbound voip dial-peer to accept the call, and then pots dial-peer that points to the FXS port. For outbound dialing from the FXS port you will need voip dial peer pointing back to CUCM.