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Ip phone and broadcast domain

Hi everyone,

I have a switch with three vlan's configured, 452 (data), 552(voice) and 198(dev).

Vlan198 is just used for a development environment. The problem I am having is that when a PC (connected to the phone) is restarted it is  getting the dhcp from vlan198 so it seems that it is listening to the dhcp broadcasts from vlan198.

I thought that with the command " switchport trunk native vlan 452" the broadcasts to the PC would be restricted to vlan452.

Can someone please clarify?

If I add the "switchport trunk allowed vlan 452,552" command I don't have the problem.

interface FastEthernet0/12

switchport trunk encapsulation dot1q

switchport trunk native vlan 452

switchport mode trunk

switchport voice vlan 552

mls qos trust dscp

auto qos voip trust

storm-control broadcast level 10.00

wrr-queue bandwidth 10 20 70 1

wrr-queue min-reserve 1 5

wrr-queue min-reserve 2 6

wrr-queue min-reserve 3 7

wrr-queue min-reserve 4 8

wrr-queue cos-map 1 0 1

wrr-queue cos-map 2 2 4

wrr-queue cos-map 3 3 6 7

wrr-queue cos-map 4 5

priority-queue out

spanning-tree portfast




Ip phone and broadcast domain

Hi Muca,

Are you running two separate DHCP servers ?? that is one on Vlan 198 and anothe ron Vlan 452 ??

If you are having two DHCP domains, it will take IP address from the server whichever replies first.

Another way to do it is change the domain name on Workstation and Vlan 452. Keep domains separate on Vlan452 and Vlan 198 ( although i doubt it will work).

Though best solution is to disallow the Vlan ( in your case Vlan 198) if you are not using it...



PS: Please rate if helpful...