remote office

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Jun 3rd, 2009
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I have a client with a UC520, would like to have a small site with 3 phones to share phone system.

Currently they have a point-to-point between the two sites.  I set the main ste up already for 4 digits.

Can someone please point me in the right direction for a paper on connecting a remote site.


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Marcos Hernandez Wed, 06/03/2009 - 20:12
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I would like to add that since this is a point to point setup, you could register the remote phones over the WAN without a VPN. That would require some manipulation of the configuration, like possibly having to disable NAT, firewall rules, edit ACL's, configuring the appropriate IP routing and static configuration of the phones (TFTP, possibly DHCP, etc.).

There are some support considerations. I have extracted the following from the documentation:

Remote skinny client control protocol (SCCP) phones connected across WAN links are
subject to the following restrictions:

–Cisco TAC will not handle any voice or signaling issues for remote IP phones, unless the
same issue can be replicated for LAN phones.

–E911 or emergency calls are not supported from remote IP phones.

–All calls made to and from remote IP phones must use G.711. Cisco CME does not support
the ability to specify G.729 codec for remote IP phones.

–For inbound or outbound calls, remote IP phones cannot fail and go over to a PSTN
connection. Remote phones must use the WAN for all calls, even if available bandwidth is
not sufficient to guarantee voice quality.

–Remote IP phones do not support Network Address Translation (NAT). All Cisco CME phones
must use IP addresses that are routeable to and from Cisco CME. Remote IP phones must be
able to access the IP addresses that are used for all other local and remote phones.

–All PSTN access is through the central site only. PSTN termination at the remote site is
not supported.

–Cisco CME does not support Call Admission Control (CAC) for remote SCCP phones, so voice
quality can degrade if a WAN link is oversubscribed. High-bandwidth data applications used
over a WAN can cause degradation of voice quality for remote IP phones.



7bridgesol Thu, 06/18/2009 - 05:44
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okay so I plugged in a 7931 on the other side of the point-to-point

The phone has received an IP from the DhCP server not the UC520

Is there any documentation on how to get the phone to receive the 10.1.1.x IP


Marcos Hernandez Thu, 06/18/2009 - 06:51
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You would need to setup a VPN. The link in my first post has some additional information.



7bridgesol Thu, 06/18/2009 - 07:30
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how would I do that when no Internet is available.  The point-to-point is all I have.

I can ping the UC520 data IP address, why could I not get an IP for the phone.

What DHCP server do you have running? Disable the DHCP server and let the UC520 do it, and there is a chance your remote phone will get an address from the UC520 over the point-to-point link, depending on the configuration.

Otherwise, just configure the DHCP server on the remote end to give out the CME address for the UC520. The remote phone does not have to be on the same LAN as the UC520, it just has to be able to get to it.

Here is an example DHCP config on a device at one of my remote sites:

ip dhcp pool REMOTE1
   option 150 ip
   option 151 ip

Depending on what kind of DHCP server you have, just set the options 150 (and i have found 151 is needed for 52x phones) to the address of your UC520.

Steven Smith Thu, 06/18/2009 - 09:14
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Are these routed networks across the point to point or do you have the same subnet on both sides?

The phone doesn't need an IP address on the 10.1.1.x network.  You will need to set the tftp address to, and you should be fine. 

Steven Smith Thu, 06/18/2009 - 09:21
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You can do it on the phone, or add it to the dhcp scope of the server that you have.  If you type it into the phone manually, you will need to set Alternate TFTP to yes on the phone, and then type the IP address into the field on the phone.

7bridgesol Tue, 06/23/2009 - 06:40
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when I go to the area on the phone for alternate tftp is will not allow me to change the setting to yes.  The only soft key available is exit.

Do I need to unlock something?

Marcos Hernandez Tue, 06/23/2009 - 08:22
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Use **# to unlock, while under the Network Settings.


7bridgesol Tue, 06/23/2009 - 09:49
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Okay so I changed the tftp server to

Under network setting it lists there DHCP server

IP address is

TFTP server

Phone is stuck with configuring IP in bottom corner of the 7931 phone.

What else could i be missing?

Per status message DHCP timeout

7bridgesol Tue, 06/23/2009 - 10:50
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okay I went in and changed the phone to have a static ip of


default router

Status message is:

tftp timeout sep0022555e85ed.cnf.xml

no ctl installed

Please advise

From the remote site I can ping uc 520 and ping which is the first phone at the main site.

Not sure what is going on now.

Steven Smith Tue, 06/23/2009 - 12:07
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Do not assign the phone a static IP in that range.  It will not work over your VPN.  Let it get the address via DHCP and leave the alternate TFTP configured.  That should do it.

Steven Smith Tue, 06/23/2009 - 12:13
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One final note, did you change the admin vlan at all?  You should not change this.

7bridgesol Tue, 06/23/2009 - 12:49
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I did not toch anything with admin vlan.  There is no VPN, it is a straight connection to the other office.  I can from a PC at the remote site, ping both data and voice networks.

Again, if I change the tftp to alternate and add the tftp server in the phone I get dhcp timeout.

If I change the ip address statically on the phone I get no ctl installed.

I think someone just posted about tftp in windows server.  Do I need their computer comapny to enter that in there server as well?

Steven Smith Tue, 06/23/2009 - 13:23
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You can use this if a windows server is providing DHCP for that subnet.  Then you would get the option 150 from the server.

Also, changing the tftp to be manually set should not effect DHCP.  Are you sure you received DHCP timeout when you manually set the IP address?  Could you have received TFTP Timeout?

If you have network setup ok, and no firewalls, you should have no problem with a UC500 ---------------- Router --------------- Phone topology.

Since ping is working, I assume that the UC500 has routes to the far end network.  From the UC500, can you ping the phone?

Steven Smith Tue, 06/23/2009 - 12:06
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Marcos is correct, press **#, you will see the lock icon open, and then you will get more options.  You can do this when you are at the Network Settings Screen before you go into other options.

nicolaagnelli Tue, 06/23/2009 - 06:56
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Hi all, i've the same problem with a remote ip phone (7970) my two lans are connected with a VPN and all it's ok, i can ping hosts each other.

The IP Phone has a static IP of remote network and as tftp server 1 the IP that the UC has on WAN Interface. The remote phone cannot register to the uc ..

What i need to change ? Than you so much for help


Marcos Hernandez Tue, 06/23/2009 - 08:23
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Wouldn't you want to point your phone to the remote LAN IP? That is what is reachable in a Site to Site VPN.


nicolaagnelli Tue, 06/23/2009 - 09:40
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sorry, but i don't understand .. my phone already point to a remote LAN ip address .. the UC has on its WAN an IP from the main LAN

and the phone is configured with tftp and router the ip on the wan of UC..

I attack a simple network layout of my net..

Thank you so much for help

Skyler Spence Thu, 06/25/2009 - 14:43
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The phone needs to tftp from, the IP for VLAN 100, not the WAN IP on the UC500

nicolaagnelli Fri, 06/26/2009 - 00:12
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ok, so i need to change my vpn ? now my vpn is between the two lans <-> not with the vlan 100..

Thank you so much

Skyler Spence Fri, 06/26/2009 - 07:00
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Just make sure that you can reach the subnet through your vpn.  Then make sure that the phone is using as its tftp server.

Steven Smith Fri, 06/26/2009 - 07:02
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You will also want the subnet through the VPN so that VM can be accessed.


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