Cascading 7940 and 7960's 1

[youcandoit]

how many phones can be connected thru the pc port with no adverse effects?

 

[neploxo]

I haven't tested a limit on that, but I have done two or three. The most important thing is to provide external power, as the first time I ever hooked one phone behind another, the excess power draw caused the 3550 switch to kill power to that port.

I would recommend plugging in a hub or switch behind the 7940/60 if you need to do this and not chaining too many phones together. They seem to work fine as far as voice VLAN is concerned, but your QoS will eventually suffer.

 

[youcandoit]

thanks neploxo. I only need to do 3 temporarily. Yes i do have external power on the addtional 2 phones. I am running the first off POE.

 

[filakio]

Can either of you tell me how to chain a phone? or is there a document out there? I have always been told it can't be done.

Thank you.
FIL

 

[rtfmdude]

You should be able to simply plug the additional phones into the PC port on the 7900s - I would just worry about the vlan interaction. Did you guys have to just set the switchport to an access vlan (for the voip vlan)?

 

[youcandoit]

The VoIP vlan is replicated thru the pc ports of the 7900 series phones. The POE is not thats why I need the extra power. At this point we are going to put in 3550's in case the customer decides he wants additional pc's or phone's. I did have one phone that we cascaded that made the whole blade began host flapping. Something about a dduplicate mac address in the cam table. we reviewed the logs traced the port to a cable and unplugged the phone. I am RMAing it to cisco tomorrow. so be careful.

 

[ADB100]

I would seriously not recommend this. Cisco only support connecting a single PC to the PC port on the 79xx IP Phones (and a PC means a PC - not a printer or appliance etc). The whole point of the PC port is so you only need a single switch port to support a user with Voice & Data. I would recommend that you increase the number of switch ports and wiring sockets as opposed to cascading devices off the PC Port on the IP Phones.

Andy