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Community Member

is ip phone really a 3 port switch?

when using a pc running sniffer,i can see the

rtp streams from the mac address of the phone

my pc(running sniffer) is attached to and the

opposite phone in conversation. I do not know

that much about it but i would think if the phone

is a switch it would have a cam table and not

send the rtp streams out the port marked pc on

the phone. i tried this on two switches a 6509

using vlan 10 as the data vlan and vlan 100 as

the aux. vlan on both ports

then again on a 3524 with a voice vlan 100

and data vlan 10. the programming was done as

per the designing cisco voip networks guide.

also i put my pc running sniffer on a port straight

into the cat 6509 the port was programmed aux vlan 100 and data vlan 10 no phone involved and i could

see broadcasts from the call manager (vlan 100)

so i am thinking that if a port is to be used

by something other than a phone i should not

program the aux vlan on it to stop this.

I hope you can help me with this because i am

confused! mainly about the rtp steams .

thanks guys! Oh and if i set up the sniffer to look

at ip addresses instead of hardware addrress i

do not see any of the above mentioned only hsrp hellos to multicast address,no phones ip address,

no rtp streams

Cisco Employee

Re: is ip phone really a 3 port switch?

The phone has a three port switch (100 uplink, 10 internal, 100 PC port), but it is inside of an embedded device and is customized for the task. The ports are switched, but the phone traffic is purposely replicated to the PC port. Interestingly enough this was done so it would be easy to attach a sniffer to the PC port to troubleshoot any problems that might be occurring between the phone and other hosts. This solution does not require a hub or to span a port on a production switch to get a sniffer trace.

Community Member

Re: is ip phone really a 3 port switch?

are there any plans to ever turn that off -- or at least let customers turn it off where they don't want nosy users seeing their phone traffic?

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