voip pabx technical faq

Can I reduce the PABX's reliance on DNS in case my DNS server dies?

What firewall ports do I need to configure?

This depends on the protocols being used. All of the rules mentioned below should be stateful, and allow response packets in or out of the firewall:

1) A standard PABX install with no external phones or VoIP links will try to use the internet to keep its internal clock correct. This uses:
UDP Port 123 (outbound from PABX)

2) If SIP phones or soft-phones are to be deployed remotely, this should be done using a VPN. The SIP protocol does not traverse firewalls at-all well. If absolutely necessary, the following ports are used:
UDP Port 5060 (inbound to PABX)
UDP Ports 2000-6000 (outbound from PABX, depending on devices used)
UDP Ports 10000-20000 (in- and outbound from PABX)
Note: Firewalls that use NAT will often cause additional problems with the SIP protocol.

3) If a SIP trunk is being used to a provider, the same ports as for SIP phones above are used.

4) If an IAX2 trunk is being used to a provider, then only a single port, which will safely traverse NAT is required: UDP Port 4569 (outbound from PABX)

5) IMPORTANT: If using a Cisco router or Firewall, you need to disable the SIP ALG (Fixup) module where possible - The Cisco SIP ALG is reportedly not compatible with non-Cisco SIP devices. The IOS commands will resemble the following:

  sip no fixup
  no fixup protocol sip udp 5060
  no fixup protocol sip 5060

6) To allow IP Cortex Ltd access to our PABX for support or maintenance:
TCP Port 22 (inbound to PABX)
This can (and should) be further restricted by specifying that these connections are only allowed from IP Cortex addresses.

Can I use a SIP phone directly over the Internet back to my PABX?

Can I use XXX's VoIP service, and how?

web interface

The web interface won't log me in.

configuring

How to configure Siemens Gigaset C460IP or C450IP

How to configure Siemens Gigaset S450IP / S685IP

How to configure Polycom IP Phones

How to configure directed pickup on a Linksys SPA962 with SPA932 sidecar

How to configure X-Lite 2.0 for Linux

How to configure Linksys ATA devices

How to configure Linksys ATA devices to support "Hook Flash" (The "R" button for trnasferring calls)

How to configure Xorcom Astribank 8

phones

The manual says our phone can be auto provisioned, but it is not working.

I cannot log-on to the web interface of my phone. What is the username and password?

I hear pops hisses and/or pauses when talking on my phone.

Phones periodically report 'NR' or 'No Service' / All my phones have stopped working

If I transfer a call to a softphone it hangs up after 30 seconds

When I talk on my phone/headset, people say I sound very quiet

I use a headset on my phone, and can hear lots of humming or buzzing.

What version of firmware should I have on my phone?

I cannot transfer calls / Transferred calls are dropped / Transferred calls don't ring for long enough to be answered.

I do not get caller ID on inbound calls.

I do not get the correct caller ID on outbound calls.

Can I use my Nokia E61 phone as a SIP Phone on your PABX?

fax

We are using a soft-fax, and some people can never get a fax to us.

We are using a FAX machine on an ATA, and it is unreliable. What can we do?

I've heard about using T.38 for faxes on digital systems. What is it, and can it help?

Is there an email-to-fax facility on the PABX?

inbound calls

Inbound calls do not work.

outbound calls

I cannot dial 100 to get the operator

I want to use a VoIP channel by default. How?

How can I calculate correct charges for calls made over the IPCortex VoIP service?

The calling number (CLI) is being sent correctly for most of my calls, but sometimes the called party sees the call coming from lowest DDI in my range instead. What can I do to fix this?

email

Email notifications of voicemail or faxes is not working

voicemail

I dial 8500 to pickup voicemail but nothing happens