Never considered this before, but a customer asked me this.

They have (20) 9608 IP phones on an IP Office. The phones are set to use vlan 2 and their data is on vlan 1.

From their computers, they can ping the IP address of a phone, even though it is in a separate vlan/network. The only way I can think that this is happening, is the WAN (LAN2) port of the IP Office is the DHCP server for the phones and the LAN port is on their data network so that it can be reached using Manager and so it can communicate with the VM Pro server.

In my mind, the IP Office is somehow bridging that connection from the data vlan to the voice vlan. How can I isolate the traffic? Customer thinks that they should be totally separate. Although they have never complained about any phone issues and I haven't noticed any call/voice issues either.