SRV records for SBC failover

[curthowland]

I've got two SBCs and would like to failover to the second if the first becomes unreachable.

The trunk registration information accepts IP address and DNS name, but not SRV record. Since these are dual SBCs, the SIP server, SIP outbound proxy, and SIP registrar are all the same. If I put in the SRV record registration simply fails.

Failover documentation that I can find all references multiple registrars, not SBC environments.

This is for NetVanta 6336 analog gateways in the field, and I've tried the latest 12.3.3 firmware.

[Anonymous]

The SRV record is handled by DNS, you just have to put the FQDN as the sip server. The DNS server of the SBC should contain the SRV record.

For example SIP trunk would look like this:

voice trunk T01 type sip

description "SOFTSWITCH TRUNK GROUP"

sip-server primary sip-server.training.adtran

The sip-server primary command can point to an IPv4 address or a hostname. Most providers have hostname pointing to a SRV record.

Then you want to create a VoIP name service (VNS)

voip name-service host sip-server.training.adtran sip udp

voip name-service verification attempts 5 interval 30

you can then see the SRV record using this command:

1. show voip name-service cache

Record Protocol Tpt Port Prior Weight Last Address

[curthowland]

"Most providers have hostname pointing to a SRV record.

I'm trying to figure out how to word this, forgive me if I seem to not get it.

I have two DNS entries, SBC-East, SBC-West, each pointing to one IP address.

The srv record, _srv_sbc-east, points to both with SBC-East listed first.

When I put SBC-East in the 6336 as the Registrar, registration works. when I put _srv_sbc-east in, registration fails.

Clearly the DNS lookup of _srv_sbc-east is not returning what is expected.

In your example,

voip name-service host SBC-East sip udp

...isn't going to do any good, because it only returns on IP address.

So would,

voip name-service host _srv_sbc-east sip udp

...be the correct form?

[Anonymous]

What exactly is your application?

Is this SIP server in the cloud to two SBCs on the customer premises and then both going to customer SIP PBX?

What is hosting your DNS?

-Mark

[curthowland]

I have one Broadsoft cluster, and two sbcs. At this point, I can register the customer premise 6336 through one, or the other, sbc, but I'd like to prefer one, and have the 6336 fail over to the other if the first is lost.

Their our own DNS servers.

[Anonymous · Accepted solution]

If all you want is your 6336 to failover from one SBC to another SBC then you can just use IPs. No need for DNS. DNS is mainly used by Service Providers in large deployments where they only have to change their sip servers in one place without having to touch all the customer devices.

voice trunk T01 type sip

description "SOFTSWITCH TRUNK GROUP"

sip-server primary 1.1.1.1

sip-server secondary 2.2.2.2

Default rollover timeout is 3 seconds.

This document goes over sip trunk failover in more detail:

https://supportforums.adtran.com/docs/DOC-4388

-Mark

[curthowland]

  sip-server primary 1.1.1.1

  sip-server secondary 2.2.2.2

Ok, since the entries are "Registrar", "Outbound Proxy" and "Sip Server", I will at this point assume that each of those gets a "primary" and "secondary" entry. Certainly doable.

Thank you. I will read the document you linked to.

[Anonymous]

Yes.

If your Registrar server is the same as your SIP Server, then you don’t need to enter it, It will default to your SIP server if not specified.

-Mark

[curthowland]

Mark,

While I had found that document earlier, the reason I asked is because the document specifically uses "sip-server", but nothing else. With your comments here, I will try it with all three entries.

[curthowland]

Excellent. Both East and West IP addresses are showing up in the "show voip name-service cache", so it looks like that was exactly what I needed. With some testing, of course.

Peace, and thank you.