IP Phone on a router and dhcp on L3

[netacaduser575395547]

Hi there 

I am trying to achive a setup where we can use ip phones. I have 4500 core switch and dhcp in it.

I set up the voice vlan and option 150 

The core does not have telephony-service. however, i have 2811 router not being used. Is it possible to use it? only for telephony-service? I dont want to create sub-interfaces for each vlans on it as i want the vlan interfaces kept in the core switch, also the dhcp.

blewo setting is an example:

In the core switch:

ip dhcp pool voice

network 192.168.100.0 255.255.255.0

default-router 192.168.100.1

option 150 ip 192.168.100.1  (on each pool of vlans)

-------------------------------------------------

int vlan 100

ip add 192.168.100.1 255.255.255.0

----------------------------------------------------------------

In access switches:

Int r f0/1-47

Sw mode access

Sw access vlan 10

Sw access voice 100

----------------------------------------------------------------

between the core and router, i tried access port,trunk port and didn't work

in the router side, i used int f0/0.100 and f0/0 and used 192.168.100.2 and 192.168.100.1 didn't work

[Flavio Miranda]

@netacaduser575395547 

 Between the Router and the switch you can use port in access and you can add the IP address to the router´s interface, you dont need subinterface. 

The option 150 on your Core switch should point to the Router IP address not the Core IP address like you did. 

 option 150 ip 192.168.100.2

Telefone you connect to the switch, will get IP address and will reach out the router based on the option 150. 

[MHM Cisco World]

Let start point by point 

Router you have can run telephony? If yes then use it IP in op150

Between SW and router use voice vlan in access port.

This make phone connect to router 

MHM

[vishalbhandari · Accepted solution]

@netacaduser575395547 Yes, it is possible to use the 2811 router for the telephony-service functionality without moving VLAN interfaces or DHCP to the router. Here’s how you can approach it:

1. Keep the VLAN interfaces and DHCP setup on the core switch, as you’ve already configured.

2. On the 2811 router, enable the telephony-service and configure it as a call manager for your IP phones. You don’t need to create sub-interfaces on the router for VLANs since the core switch will handle inter-VLAN routing and DHCP.

3. Connectivity between the core and the router: Use a trunk port on the core switch and the router to pass the voice VLAN traffic. On the router interface, use the native VLAN (default) for communication and the router can provide telephony services to devices in the voice VLAN.

[netacaduser575395547]

Hi

Thnak you. it works. 

i had to use sub-interface in order to use dot1Q. Also, if i use (encapsulation dot1Q 100 NATIVE) it woun't work. only work without the word native

My last 2 question is how do i choose the number for a spicific phone?

Also, what does auto-reg-ephone do?

I have attached the router config

Many thanks

[Mancunian]

auto-reg-ephone feature simplifies the deployment of IP phones by automatically registering them to a Cisco Unified Communications Manager Express system. While useful for provisioning and testing, it should be carefully managed to avoid unauthorized device registration in production environments.