C-series endpoints and SRV registration

[Greyhead89]

We've just clustered our two VCSs and set our endpoints to register with a cluster domain.  The SRV is setup and operating fine on our MXP units, but the C-series fail to look up the DNS record and fail to register.  What is the difference between the lookkup process between the units?

xstat h323

*s H323 Gatekeeper Status: Rejected

*s H323 Gatekeeper Address: ""

*s H323 Gatekeeper Port: 0

*s H323 Gatekeeper Reason: "DNS lookup failed"

[Patrick Sparkman]

Hello Gordon -

Are your endpoints assigned an IP via DHCP or static?  If static, did you also specify at least one DNS address?

[Greyhead89]

Hello Patrick

endpoints are all on static IPs, and DNS servers are statically set as well.  DNS lookup works fine on the C-series units; they can successfully look up the DNS of the VCSs directly and register, but when they look up the cluster SRV they fail.

[Patrick Sparkman · Accepted solution]

What are your SRV records for the cluster, maybe you have one configured wrong.

[Greyhead89]

(wrongly clicked 'Correct Answer to the above')

SRV Records as below (xxxxxx is our domain).  We only use H323 on our network at the moment.

SRV record is vcsccluster.euk.xxxxxx.com

Records are:

1 1 5061 vcsc.1.euk.xxxxxx.com

1 1 5061 vcsc.2.euk.xxxxxx.com

1 1 5060 vcsc.1.euk.xxxxxx.com

1 1 5060 vcsc.2.euk.xxxxxx.com

1 1 1719 vcsc.1.euk.xxxxxx.com

1 1 1719 vcsc.2.euk.xxxxxx.com

1 1 1720 vcsc.1.euk.xxxxxx.com

1 1 1720 vcsc.2.euk.xxxxxx.com

thanks

[Patrick Sparkman]

What are the rest of the records, the service and protocols?

Example:  _h323rs._udp.domain.com

[Patrick Sparkman]

You can check the following document, that might help.

https://supportforums.cisco.com/docs/DOC-25395

It sounds like you're missing the _h323rs record, which is used for registrations.  That document can explain SRV records for use with the VCS.

[Greyhead89]

That's sorted it!  The _Service._ProtocolTTL Class SRV PriorityWeightPort Target records weren't in the table at all.  All C-series now registering fine.

many thanks.

[Greyhead89]

the next problem is that our Codian MCUs (4515 and 4520) won't register using h323 to the cluster SRV.  They work fine directly to the DNS of the peers or the master.  Do they support it?

[Patrick Sparkman]

I don't think they support SRV records, as I haven't seen any documentation on it at least.  What I would recommend is under the cluster domain, create two DNS A records, one for each peer.  That way if something tries to register or call via the cluster domain, if they don't support SRV records, they can fall back to either of the peer IPs.  The two A records would be setup in a round robin.

[Tomonori Taniguchi]

MCU doesn’t support H.323RS SRV for gatekeeper registration process.

If you must to have redundancy and alternative GK functionality on MCU, you might want to enable embedded GK then configure neighbor gatekeeper (you can configure 2 GK IP address on MCU as neighbor peer).

Remember you will then need to create neighbor zone on VCS pointing to MCU and search rule since MCU no longer registered on VCS with this method.