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New Member

IP phones in a Cisco network

I've done alot of network programming in the past. At that time, what I'm discussing wasn't possible. But I now have a client that needs this. Maybe Cisco has some product I'm not aware of.

The problem is that this client has a large network of IP phones on their IPv4 LAN. They want to know which gateway the phone was connected to. And the network address of each phone. They need the network address for reporting purposes.

One solution I thought of was to use a "traceroute" type of query. And assume that the device one hop from the phone is the gateway.

However, I have to know the subnet mask in order to determine network address. This client wants automatic discovery, so I'd have to discover the subnet mask on the fly. When I say "subnet mask", I'm talking CIDR.

My questions are:

1) Has Cisco ever gotten around to providing such information in a centralized product? Ideally, this router/gateway information would be provided in a central place. And I could query it from an external program.

2) I know in the past, it wasn't possible to determine subnet mask without using SNMP. Is this still my only other option?

  • IP Telephony
New Member

IP phones in a Cisco network

Hi Brice,

Cisco phones easily display all this info. Where do the phones register? CUCME or CUCM?

In both systems you can view registered phones, this will tell you their IP address and MAC address plus phone number. Someone may have configured a user name also.

The default gateway would be issued by DHCP. You can also go into the settings on the phone and view the leased IP address, mask and gateway, DNS and TFTP server information. You can also view the Call Manager list and which one it is registered to.

So, 1) yes, Cisco UCM are centralised.

2) Unless every device is statically configured with IP information, then you would normall derive this info from the configured DHCP scope.

Also, the DHCP server (scope) will issue TFTP server info, which in turn will provide the Call Manager to register to. You could go quite deep into this if you wish to know more. I recommend looking up how a Cisco phone registers with a Call Manager.

New Member

IP phones in a Cisco network

Thanks for the info. Being able to view the data on the phone or in UCM is different from programatic access (API).

Just trying to determine what info I can read over the network. I mentioned SNMP because they aren't going to provide me with IOS logins for all the phones, gateways, etc.

Super Bronze

IP phones in a Cisco network

Hi Brice

You would need to do the following:

1) Connect to the RIS API on CUCM and retrieve IP addressing information for the phone from there. You might first connect to AXL to retrieve a list of IP phone device names which you would use to query RIS.

2) Once you have the IP addresses, you can get the network mask information and CDP connection info from the phone's web server. Browser to the phone, and you see various web pages iwth the information. In most cases, adding X to the end of the URL makes it return XML rather than HTML (e.g. DeviceInformation versus DeviceInformationX)

The CDP info and subnet mask won't be available from CUCM, it will know only the IP address.

More info in the API guides for CUCM:


Aaron Harrison

Principal Engineer at Logicalis UK

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Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
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