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

Wes Sisk wsisk at cisco.com
Mon Sep 28 15:48:30 EDT 2009


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 <mailto: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> <mailto: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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>
>
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>
>
>
>             -- 
>             Ed Leatherman
>
>
>
>         _______________________________________________ cisco-voip
>         mailing list cisco-voip at puck.nether.net
>         https://puck.nether.net/mailman/listinfo/cisco-voip
>
>
>

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