trying to set option 150 in DHCP

Unanswered Question
Nov 18th, 2008

Cisco 2651XM router

IOS = c2600-adventerprisek9-mz.124-2.T.bin

I'm having great difficulty getting a cisco 7940G phone working - I've got 'Protocol Application Invalid' on the display. None of the phone buttons work except the factory reset procedure, which just produces the PAI message again.

I read on google that I have to have set option 150 on the DHCP. My 2651XM router is my DHCP server but it won't accept the command:

router(config)#dhcpd option 150

it comes back with

'% Invalid input detected'

Is this because I'm not using a voip IOS? or is there some other reason? I think I've found the ip address of the phone but I can't tftp it or anything. I'm stuck, thanks for any pointers.

I have this problem too.
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Mark Yeates Tue, 11/18/2008 - 17:04


Please see the following example.

ip dhcp pool test


option 150 ip





tonyspcrepairs Wed, 11/19/2008 - 08:27

thanks for your response Mark, I applied the settings you gave to the FastEthernet0/0 port of my router, and connected the phone to this port via an external hub.

I gave F0/0 ip address and the phone display said 'Requesting Configuration' and then it switched to 'TFTP timeout'. So the phone is expecting to download something via tftp but I'm not sure what to do next. I've ascertained the phone has ip address

thanks for any further help.

Mark Yeates Wed, 11/19/2008 - 15:51

When I typed out the example it wasn't quite ready for copy and paste into a router. You will want to exclude the default gateway, TFTP server, and the DNS server IP's from the scope. I would also flip flop the phone IP and fa0/0 IP addresses. Give the phone and configure fa0/0 with The problem you had was the DHCP address your phone pulled was pointing to itself as the default router. I would also include the following statements in your router.

ip dhcp excluded-address

What is the IP of your call manager? ensure the IP address of the call manager is configured as the option 150 IP address in your DHCP scope.




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