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New Member

Prob. in cisco 7902 & 7940 IP Phone


Plz, help me which port I am to open in router for all of those IP Phone.



Hall of Fame Super Silver

Re: Prob. in cisco 7902 & 7940 IP Phone

Hello Tarun,

I try to guess that you want to support Cisco IP phones on your network.

On the LAN switch ports you should configure a voice VLAN (for example vlan 50).


interface fas0/11

desc example for Cisco IP Phone


switchport mode access

switchport access vlan 10

switchport voice vlan 50

You need to define vlan 50 on your switches.

At the router level what you need to configure is an helper address command pointing to the DHCP server.


int gi0/1.50

enc dot1q 50

ip address

ip helper address

On the DHCP server you need to define a scope for network with option 150 to define the tftp servers used by the phones.

the tftp servers are the CallManager servers or some of them. The phones need to contact the CM servers in order to work: to download the latest firmware, to register themselves etc.

Hope to help


New Member

Re: Prob. in cisco 7902 & 7940 IP Phone


Actually due to access-list, all ports are block except ports 80,67,68,69 and 2000.

When I started my IP Phone, it's getting IP from CM but not working properly.

I think need to open more ports. This is the problem.



Hall of Fame Super Silver

Re: Prob. in cisco 7902 & 7940 IP Phone

Hello Tarun,

now is is more clear. I'm sorry but I tried to guess.

So how to modify your access-list: you need to permit DCHP, TFTP, TCP port 2000 the skinny protocol (SCCP) but you need also to allow communication between the IP phones and phones located on other IP subnets (the bearer channel in a VoIP communication= the voice packets). They use RTP protocol (realtime transport protocol) that is built upon UDP. RTP uses a wide range of UDP ports and its companion control protocol RTCP too.

"RTP does not have a standard TCP or UDP port on which it communicates. The only standard that it obeys is that UDP communications are done via an even port and the next higher odd port is used for RTP Control Protocol (RTCP) communications. Although there are no standards assigned, RTP is generally configured to use ports 16384-32767/UDP"

Use the following link for a complete reference of protocols involved in CCM 4.1:

Hope to help