SBC-trunk down following IP change

[Dominique_CH]

One of our customer operates an on-premises 3CX V18 w/ following characteristics:
- 3CX has a fixed IP
- Remote SBC is behind a router which changes IP once in a while (no fixed IP on operator side)
He experiences the effect that the trunk goes down upon IP-change (which is fine due to the IP change), but it takes about 10 minutes to come back up. There are only 5 IP-phones connected to that SBC.

I'm wondering whether such long delay is to be expected and whether there are ways to speed up the process.

 

[TheodorosG_3CX]

The SBC requires to be able and fully resolve the FQDN in order to register. You might need to consider a static ip to avoid this situation.

 

[Dominique_CH]

This isn't the problem as the 3CX does have a fixed address.

 

[SweetAction]

If you restart the SBC service (you don't mention Windows or Linux), does it come up right away?

Alternatively, if you restart the whole box, does it come up right away?

 

[Dominique_CH]

@SweetAction : Probably yes in both cases (it's a Linux box), but I'm not watching this connection permanently, so impossible to verify

 

[Dominique_CH]

According to 3CX documentation, an SBC requires a static IP. However, we noticed that an SBC behind an operator-router which gets its address assigned via DHCP is fine as long as its address doesn't change too often. Upon router-address change, however, the SBC looses its connection to the PBX and re-connection takes, for some strange reason, around 10 minutes.

 

[SteveITS]

an SBC requires a static IP

That's more for the SBC itself, since phones use the SBC LAN IP as their proxy and if it changes they are pointing to the wrong IP.

I have not noticed your problem on any clients, however, around here most businesses use Comcast/Xfinity cable and Comcast normally does not change a public IP that is in use. Unlike, say, AT&T who used to do it quite a lot to me at home when I had DSL several years ago.

However we do have one client with two WANs, and their SBC will move between them without a long outage. It doesn't email a "down" alert, only the "up" email with the new IP. That's running as a VM.

 

[ivank]

Hi Dominique_CH,
is it possible to enable verbose logging for SBC and provide the log files next time it happens?
Due to the file size you'll have to upload it somewhere and share the link in a PM with me.
I will try to find out why it takes this long.