Implemented Redundant SBC Support

[cobaltit]

I'd like to see support for redundant SBCs. So this would be two SBCs devices at the customer premise and both IP's entered into the provisioning tab of the extension. This would cause the 2nd (backup) SBC to be provisioned as SIP Server 2/Outbound Proxy Server 2 in the account (or as a second account, not sure which is better).

 

[cobaltit]

It does work. Been doing it for a while.

 

[BrenttG]

It does work. Been doing it for a while.

I mean as far as, setting up 2 identical SBCs, pointing a single DNS name to both of them, and then setting up a few phones, and once we see phones on both of them, yank the power on one SBC, and see if the phones all jump to the other seamlessly.

 

[cobaltit]

Yep, it works.

 

[contoured]

+++1111 Big bump

 

[Tony Cave]

BUMP... I see the workaround apparently works, but integrated into the 3CX would make more sense.

Also @cobaltit does this workaround work with the new SBC software provisioned via the console??

 

[BrenttG]

BUMP... I see the workaround apparently works, but integrated into the 3CX would make more sense.

Also @cobaltit does this workaround work with the new SBC software provisioned via the console??

This is not something that is likely to be "provisioned in the console" as 3CX does not control your local dns server. But this isnt a "workaround" either, this is exactly how DNS is supposed to work, right down the the RFCs, particularly RFC 1794. https://tools.ietf.org/html/rfc1794

 

[Tony Cave]

@BrenttG, understand that this is how DNS works, sorry if my comment was unclear, I was wondering if 3CX could simplify this into the console of 3CX somehow to negate the need to mess around with the Local DNS server... Maybe a primary and secondary SBC option under the provisioning tab of the phone??

 

[BrenttG]

Unfortunately i am not familiar with any phone model that allows for multiple SBC Addresses in its settings, yealinks surely dont, but why should they since if you use DNS you can have any many as you want. With DNS, you could have 2 SBCs, or 10.

If you want to get really technical, you arent even "required" to use internal DNS, you can use external, just so long as you dont use the same record between multiple locations with SBCs, sbc1.mydomain.com for 2 SBCs are 1 location, and use a sbc2.mydomain.com for the next sites sbcs. It is best practice to use the local dns for these types of things, however using external works also with the exception of if a phone switches offices, you will have to change its provisioning to the other SBC's name and factory reset it. Where as with local, just set the record at each location to the appropriate ip for that location, then they could share as long as the DNS of each site isnt shared or linked to active directory or the such.

 

[Tony Cave]

Thanks for your input BrenttG, it's been super helpful

 

[BrenttG]

Editted previous post to add more.

 

[drewt]

+1
All my 3cx systems use Yealink T4x models, and all of them have redundant sbc's set in the proxy field, which has two entries, but I have to do it manually and am always worried that a reprovision will wipe the setting. Lets get this one over the wall!!

 

[BrenttG]

in any case, setup a set of A records, which takes 60 seconds, then your done and it works from inside 3cx even.

 

[Nick W]

So i havent tried it, but this may already be possible just based on DNS standards already in place, i may have to conduct an experiment to test the theory, but if you were to setup 2 SBCs and on the local DNS server at the site with the phones, setup an A record for each SBC, but with the same name.

A sbc.company.local 10.0.0.5
A sbc.company.local 10.0.0.6

and then instead of using the IP of the SBC in the 3CX provisioning tab, instead specify the local DNS name. from the DNS prospective this should work perfectly, and the phones will use either SBC essentially at random, and if one dissappears, should in theory use the other one. This is how services online such as google handle their search web servers, example, do a nslookup of google.com, and you are provide multiple IPs to try, your browser picks one and tries it, if no response, it tries another.

This behavior is standard practice for DNS protocols, its not something specific to a web browser.

I would agree that this should be possible.I need to test this!

 

[Nick W]

Sorry, the forum hid other replies. I see others have this working.

This should be the standard I think. I am trying to figure out if there are any pitfalls (outside DNS failing)

 

[N_G]

In update 4

 

[dandenson]

Hey @Nick Galea , can you give more details on how this will be implemented?

 

[BrenttG]

most likely they just allowed for duplicate/multiple SBC addresses in 3cx itself for the sbcs.

 

[ivank]

For those interested, we use corosync/pacemaker stack with virtual IP. More details will follow in due time.

 

[BrenttG]

For those interested, we use corosync/pacemaker stack with virtual IP. More details will follow in due time.

Interesting choice given that DNS already made this work....

 

[dandenson]

@BrenttG - the problem with DNS is that you are stuck living with the TTL, so if you put an SBC's fqdn and handle in DNS, the phones will still honor the TTL and you will have a delay.

Using corosync/pacemaker to migrate the IP address between active SBC is WAY faster. Interested to see how sessions are handled or if an SBC failver amounts to a dropped call and the phone re-registering.