CUP 7 - CUCM 7 & DNS SRV Config

Unanswered Question
May 27th, 2010

Does anyone have the actual configuration examples for enabling DNS SRV in CUCM and CUP 7.x to support high availability?  I have read through all the Cisco docs which seem to be lacking in specific CUCM/CUP configuration examples and which, if any service parameters in CUP need to be changed.

Thanks,

Jeremy.

I have this problem too.
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htluo Thu, 05/27/2010 - 14:29

It depends on what "example" are you looking for.

Cisco does not have documentations on SRV examples because it's actually out of Cisco scope.

Basically, you may treat SRV as a container for multiple A records with additional information like priority, service ports, etc.  See http://en.wikipedia.org/wiki/SRV_record

If you have two CUPS servers, cup1.acme.local and cup2.acme.local, you would configure SRV record like below:

_sip._tcp.acme.local. 86400 IN SRV 10 60 5060 cup1.acme.local.
_sip._tcp.acme.local. 86400 IN SRV 10 20 5060 cup2.acme.local.


For explanation of the numbers above, see Wiki.

Michael
http://htluo.blogspot.com

jledbett@allegi... Thu, 05/27/2010 - 14:35

I have all the DNS info configured, was more looking for what gets added to CUP / CUCM...

1.  Obviously in CUCM, DNS SRV needs to be selected for the CUPS SIP trunk, but does it need the FQDN with the service/protocol or without?  Also does it use TCP or UDP on port 5060?

2.  In CUP do any service parameters need to be updated, such as setting the balancing to SRV and populating the domain proxy field with the DNS SRV entry and if so, which FQDN?

3.  The CUPs presence gateway settings would be changed to the DNS SRV, but does it need the TCP or UDP FQDN?  And which FQDN type - with the service/protocol or without?

Thanks,

Jeremy.

htluo Thu, 05/27/2010 - 14:41
1.  Obviously in CUCM, DNS SRV needs to be selected for the CUPS SIP  trunk, but does it need the FQDN with the service/protocol or without?   Also does it use TCP or UDP on port 5060?

[Michael] In CUCM, you use the SRV record.  In our example, that would be "_sip._tcp.acme.local" (without quotation marks).  You don't specify ports.  Because the ports are specified in the SRV record itself.

2.  In CUP do any service parameters  need to be updated, such as setting the balancing to SRV and populating  the domain proxy field with the DNS SRV entry and if so, which FQDN?

[Michael] No configuration required on CUP.

3.  The  CUPs presence gateway settings would be changed to the DNS SRV, but does  it need the TCP or UDP FQDN?  And which FQDN type - with the  service/protocol or without?

[Michael] I don't think CUP presene gateway supports SRV.  I'll double check.

Michael

Jonathan Schulenberg Thu, 05/27/2010 - 15:26

I have the presence gateway configured as a SIP SRV record in CUPS 7.0(8) and the help documentation specifies that an SRV record is supported. I have it as "_sip._tcp.domain.domain.local"

Presence Gateway: FQDN, DNS SRV FQDN, or the IP address of the associated  Cisco Unified Communications Manager server or Microsoft Exchange  server.

148west@gmail.com Fri, 06/17/2011 - 12:06

hi micheal

i am integrating cucm with cups, as far as i know with dns srv i have entered following information

domain=rabbit.com

service=_sip

protocol=_tcp

priority=0

weight=100

port number= 5060

host offering this service=cups

this srv record _sip._tcp._rabbit.com i have entered in cucm sip trunk page.

now in cups i have to add srv record for service pointing to cucm, this is what i have enterered.

domain=rabbit.com

service=_sip

protocol=_tcp

priority=0

weight=100

port number= 5060

host offering this service=cucm

now when i add srv record i am getting error.

"Presence Gateway - value must be either a valid Hostname or IP address."

now let say if it does allow me to enter the srv record, how it will decide which host to go to. cups or cucm.

regards

Christos Georgiadis Fri, 06/17/2011 - 16:36

It depends on what version of CUPS you are using. From what I remember in the latest releases you need to use simply the fqdn name without the _sip._tcp part.

It is always recommended to put these records in a subdomain so as to avoid any conflicts with any other srv records configured.

HTH,

Christos

148west@gmail.com Fri, 06/17/2011 - 16:48

hi chirs

first thanks for your reply

i am using cups 8.5 and cucm 8.5

do you recommend using srv or FQDN for sip trunk and presence gateway.

As for the first part, if i decided to use srv, my entry in dns should look like this.

domain=cups.rabbit.com

service=_sip

protocol=_tcp

priority=0

weight=100

port number= 5060

host offering this service=cups

and for cucm

domain=cucm.rabbit.com

service=_sip

protocol=_tcp

priority=0

weight=100

port number= 5060

host offering this service=cucm

correct me if i am worng.

regards,

note: in the presence gateway configuration help it does say to use srv record.

Jonathan Schulenberg Fri, 06/17/2011 - 16:45

SRV records do not work the way you have configured them. At each domain level only one product (e.g. CUCM or CUP) can use that SRV service for a particular protocol (e.g. SIP). It will not work as you have it because you have created SRV records for _sip._tcp and pointed it to two separate products!

You need to create subdomains for each product. Here's the output of one working example using nslookup:

Here are the records for CUP. Note that they are in the subdomain presence.uc.domain.com.

Based on this you would enter "_sip._tcp.presence.cluster1.uc.domain.com" into the Destination Address of the SIP Trunk in CUCM and check the SRV checkbox.

nslookup

set type=srv

_sip._tcp.presence.cluster1.uc.domain.com

Server:  dns-server.domain.com

Address:  10.242.40.64

_sip._tcp.presence.cluster1.uc.domain.com  SRV service location:

          priority       = 10

          weight         = 0

          port           = 5060

          svr hostname   = presence2.cluster1.uc.domain.com

_sip._tcp.presence.cluster1.uc.domain.com  SRV service location:

          priority       = 10

          weight         = 0

          port           = 5060

          svr hostname   = presence1.cluster1.uc.domain.com

presence2.cluster1.uc.domain.com   internet address = 10.245.250.58

presence1.cluster1.uc.domain.com   internet address = 10.245.250.57

Here are the records for CUCM. Note they are in the subdomain uc.domain.com.

Based on this you would enter "cluster1.uc.domain.com" into the presence gateway on the CUP server.

nslookup

set type=srv

_sip._tcp.cluster1.uc.domain.com

Server:  dns-server.domain.com

Address:  10.242.40.64

_sip._tcp.cluster1.uc.domain.com  SRV service location:

          priority       = 10

          weight         = 0

          port           = 5060

          svr hostname   = manager5.cluster1.uc.domain.com

_sip._tcp.cluster1.uc.domain.com  SRV service location:

          priority       = 10

          weight         = 0

          port           = 5060

          svr hostname   = manager6.cluster1.uc.domain.com

manager5.cluster1.uc.domain.com   internet address = 10.245.250.37

manager6.cluster1.uc.domain.com   internet address = 10.245.250.38

PS- Christos is correct. The behavior appears to have changed in recent CUPS versions; it no longer wants _sip._tcp in the URL even though this isn't clearly documented.

Christos Georgiadis Fri, 06/17/2011 - 16:55

Great example. I couldn't have written it better!

On top of the above just watch out for the following defect which you will probably hit when using SRV records

CSCth25928

Callmanager will never try the second SRV record if the primary CUPS is down

Doesn't look it's fixed yet.

Regards,

Christos

Jonathan Schulenberg Fri, 06/17/2011 - 17:08

Wow. How/why is that classified as an enhancement request and not an defect?! That essentially renders all SRV usage on CUCM completely pointless!

mbuttnerMSI Tue, 01/03/2012 - 23:05

Does this bug make CUPS HA pointless as DNS SRV is required for the functionality being described throughout this thread?Two sites with both a CUCM and CUP, and the active site goes down. Will the presence gateway work?

I understand the Jabber/CUPC clients will failover to the second CUPS server but then there is no Presence gateway for soft and hard phone and presence status.

Has this been resolved in 8.6 latest? The bug does not indicate such and I opened a TAC case to see but wanted to see if anyone has been successful in a CUCM/CUPS failover.

Thanks

jhardy Tue, 05/15/2012 - 11:54

As of today May 15, CSCth25928 is not resolved.  I recommend using the bug toolkit to track the progress of any bug.  Here's a link for your convience.

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCth25928

There is now a workaround in the bug.

Workaround:

Configure two A records that point to the CUPS pub and sub by configuring a

dummy fqdn in DNS where the cucm sip trunk is pointing at. This dummy fqdn

resolved into 2 ip addresses.

Now the caveat is that you have to configure this fqdn in the cup sip proxy

service parameter

Server Name (supplemental)

In order for cup server to recognize that this fqdn is destined for CUP

otherwise we endup in a loop.

-- Joseph Hardy

Schwaby81_2 Wed, 06/06/2012 - 12:20

So if I'm understanding this correctly, the Destination is an SRV option for a SIP trunk in CUCM is nothing more than a cosmetic button? It actually doesn't work until the feature is "enhanced"??



jhardy Wed, 06/06/2012 - 13:25

To answer both of your questions...  Yes this functionality is broken, which is why we have a bug filed.

Just getting in to semantics here, but I wouldn't use the words cosmetic nor enhancment to describe the problem.  Cosmetic implies there is no effect beyond what you see, and ehancment typically means we are going to add some functionality to the product.  This is not cosmetic, because selecting the SRV option will change CUCM's behavior.  Specifically, it will query for an SRV record, not an A record.  And if there is no SRV record in DNS it won't work at all.  This is not an enhancment request, because this is a deviation from the designed behavior.  We aren't adding some new functionality, just getting what should be there working.  This is just a bug that needs fixing.

-- Joseph hardy

srichardson@epl... Mon, 12/03/2012 - 14:21

Jonathan and Joseph,

Thanks for your supportive answers here.  I have two questions.

1.  The DNS SRV record example is great, but I'm confused.  If I need to also add a DNS SRV record for the Jabber client auto resolution, is this a separate record?  I'm thinking so, but am doing my first install.  If I'm right, then for HA I would want 3 records - one for the Presence Cluster for HA (subject to the BUG), one for the CUCM cluster for resiliency of the Gateway and then one for the Jabber Clients...right?

2. The bug is not fixed yet, is it?  BugTool Kit seems unresolved.  Can you help me with a sample FQDN naming convention for the cluster DNS SRV record and for the Supplemental work around record?

Here is the example from the guide:

DNS SRV Records

You must add a DNS SRV record for the _cuplogin service name in the DNS server on the presence server

domain. If this DNS SRV record does not exist, Cisco Jabber for Windows cannot perform DNS SRV lookups.

The following is an example of a DNS SRV record:

_cuplogin._tcp.company.com

Server: dns_server.company.com

Address: 10.10.1.10

_cuplogin._tcp.company.com SRV service location:

priority =0

weight =0

port =8443

srv hostname =cupserver.company.com

internet address =10.53.56.57

In the preceding example, _cuplogin is the service name. The presence server domain name is company.com.

The SRV record defined in the DNS server for the company.com domain is _cuplogin._tcp.company.com.

Cisco Jabber for Windows 9.1.x Installation and Configuration Guide

38

Plan for Cisco Jabber for Windows

Automatic Server Discovery

Note Cisco Jabber for Windows

• Uses port 8443 by default, not the port that is mapped in the SRV record.

• Supports weight and priority during DNS SRV lookup.

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