[cisco-voip] DNS client on CUCM, Unity servers?

Mon Sep 28 16:03:13 EDT 2009

Thanks Wes. This really highlights the requirements. I notice the bug you pointed out was only for an upgrade though. Not for actual operations. Do you think CUCM/informix won't start up without DNS after a normal restart? 

--- 
Lelio Fulgenzi, B.A. 
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1 
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN) 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
"Bad grammar makes me [sic]" - Tshirt 

----- Original Message ----- 
From: "Wes Sisk" <wsisk at cisco.com> 
To: "Lelio Fulgenzi" <lelio at uoguelph.ca> 
Cc: "cisco-voip mailinglist" <cisco-voip at puck.nether.net>, "Ed Leatherman" <ealeatherman at gmail.com> 
Sent: Monday, September 28, 2009 3:48:30 PM GMT -05:00 US/Canada Eastern 
Subject: Re: [cisco-voip] DNS client on CUCM, Unity servers? 

Good points, DNS required for reverse resolution of SIP endpoints. Most presence deployments will use CUPS which has heavy AD dependence which will require AD which will necessitate DNS. In short, yes, presence will likely require DNS as well. 

NAT explanation: 
Whatever is configured under system->server is what gets populated into TFTP configuration files passed to devices. Since there is nothing out there to fixup XML, and especially encrypted/signed XML files, the hostname would be passed to endpoint. Endpoint would attempt DNS resolution. That DNS query would be fixedup to return the outside IP of CUCM. If you specified an IP under system->server the endpoint would attempt to contact that IP directly. You could only redirect/NAT that session if you controlled IP routing in the remote subnet. DNS fixup is a more friendly/transparent option. 

AD explanation: 
AD sync must be configured with servername. Name to IP resolution requires DNS. 

/Wes 

On Monday, September 28, 2009 3:43:34 PM, Lelio Fulgenzi <lelio at uoguelph.ca> wrote: 

Yowza - Can you elaborate on what you mean by NAT and/or AD? 

    • Endpoints doing NAT somewhere out there? Not sure why you'd need DNS for that. 
    • As for AD, do you mean AD/LDAP integration/synchroniation? 

I would have though you need DNS for SIP endpoints, presence, etc. 

--- 
Lelio Fulgenzi, B.A. 
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1 
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN) 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
"Bad grammar makes me [sic]" - Tshirt 

----- Original Message ----- 
From: "Wes Sisk" <wsisk at cisco.com> 
To: "Lelio Fulgenzi" <lelio at uoguelph.ca> 
Cc: "cisco-voip mailinglist" <cisco-voip at puck.nether.net> , "Ed Leatherman" <ealeatherman at gmail.com> 
Sent: Monday, September 28, 2009 3:40:39 PM GMT -05:00 US/Canada Eastern 
Subject: Re: [cisco-voip] DNS client on CUCM, Unity servers? 

If doing NAT or AD it is required. Otherwise it is still a liability. Example: 
CSCsw88022 Database should still start and function when DNS is unavailable 

In this case Informix will not start if configured DNS servers are unreachable. 

/Wes 

On Monday, September 28, 2009 3:33:41 PM, Lelio Fulgenzi <lelio at uoguelph.ca> wrote: 

interesting. is the recommendation still to not enable DNS on CUCM servers? 

--- 
Lelio Fulgenzi, B.A. 
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1 
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN) 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
"Bad grammar makes me [sic]" - Tshirt 

----- Original Message ----- 
From: "Wes Sisk" <wsisk at cisco.com> 
To: "Lelio Fulgenzi" <lelio at uoguelph.ca> 
Cc: "cisco-voip mailinglist" <cisco-voip at puck.nether.net> , "Ed Leatherman" <ealeatherman at gmail.com> 
Sent: Monday, September 28, 2009 3:31:18 PM GMT -05:00 US/Canada Eastern 
Subject: Re: [cisco-voip] DNS client on CUCM, Unity servers? 

yes, but the dependence on DNS will still affect you intermittently. 

/wes 

On Monday, September 28, 2009 3:28:57 PM, Lelio Fulgenzi <lelio at uoguelph.ca> wrote: 

Wes, 

Can we enable DNS but still program the IP address of the CUCM nodes ? 

--- 
Lelio Fulgenzi, B.A. 
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1 
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN) 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
"Bad grammar makes me [sic]" - Tshirt 

----- Original Message ----- 
From: "Wes Sisk" <wsisk at cisco.com> 
To: "Ed Leatherman" <ealeatherman at gmail.com> 
Cc: "cisco-voip mailinglist" <cisco-voip at puck.nether.net> 
Sent: Monday, September 28, 2009 3:26:26 PM GMT -05:00 US/Canada Eastern 
Subject: Re: [cisco-voip] DNS client on CUCM, Unity servers? 

Enabling DNS will affect all operations. It's not a component-wise defined feature, think all or nothing. 

All code calls gethostbyname(), gethostbyip(),gethostentry().. which invokes host name resolution features. 

Just make sure: 
1. forward resolution for all servers work 
2. reverse resolution for all servers work 
3. all servers use same dns suffix 

CLI 'set network dns...' is the command set to set and enable dns. 

/Wes 

On Monday, September 28, 2009 3:09:26 PM, Ed Leatherman <ealeatherman at gmail.com> wrote: 

Follow-up question about DNS.. 

Originally I did not enable DNS on any nodes, as it was not needed. I would now like to configure an SMTP server for alerts, and our systems group wants me to use a name instead of IP. Are there any ramifications to turning on DNS, regarding things like database replication or intracluster communications? My servers are all defined by IP addresses, so it should be using that through-out, right? 

I'm assuming various "set network dns*" commands will turn this on if I decide to do that. 

On Tue, Aug 18, 2009 at 10:46 AM, Wes Sisk < wsisk at cisco.com > wrote: 

On the surface this seems an odd question so I'm sure there is misunderstanding. 

CM needs access to DNS to perform forward and reverse lookups on: 
SIP endpoints 
h323 endpoints 
AD servers 
other nodes in the cluster 

There are deployments which do not use any of these and therefore do not need access to a DNS server. On those, DNS can be disabled. 

/Wes 

On Tuesday, August 18, 2009 1:54:37 AM , ciscozest <ciscozest at gmail.com> wrote: 

We have 3 CUCM 7.0 servers and only one Unity Connection 7.0 server. 

We use a load balancer for IP Phone services redundancy. There is no integration with any third party components. When I check our UC system, I found out that DNS client service is enabled on both CUCM and Unity servers which I don’t quite understand why is needed. The Services URL on CUCM is pointing to load balancer IP. Would there be any other reason we have to enable DNS client on CUCM and Unity server? Also is there a load impact by enabling DNS client service? 

Thank you. 
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Ed Leatherman 

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