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Cannot reach PBX system using data network

Good day Cisco people,

I am Simon and I have a big situation. My company recently expanded to one of our branches. Now this branch houses 100-150 employees. They are using computers and IP phones.

Currently, Our voice and data are integrated into one network.( With no configuration for voice and data vlan on the 5 Cisco switches that distributes the broadcast). We have a Cisco 1941 router used for DHCP for our local data lan and for VPN connection to our Head Office, It's network id is Then for the IP Telephony we have Avaya 500 v2 for the PBX, It's network id is

Now here is the problem and the questions.

1. I cannot reach the Avaya PBX from the Cisco Router even though I added a static route from the router. ( Do I need to add the route also from the PBX to the router? I want to add that I don't have any experience in voice networking only in data networking.) And is there a way/or is it possible that I could add a route from PBX to router?

2. If I am going to configure two vlans on the switches for the data and voice vlan? Do i need to configure router on the stick on the router? How about the interface that the PBX is connected to? what should I configure it? Should I configure it as a voice vlan only? a trunk port? access port?

3. Lastly, what could be possibly go wrong if ever I configured this on a production environment? And is it that hard to integrate voice with data?


Thank you for your support. I hope you understand. I don't have experience yet in handling both voice and data. Only data networks.

Note: Attached also is a simple network diagram for reference. Thank you.

Have a nice day,



Hi Simon,I assume your phones

Hi Simon,

I assume your phones are using static IP addresses to allow them to talk to the PBX?

If your switches have no VLAN configuration then you will have both layer 3 subnets running over the same layer 2 VLAN.

You could do a quick test and put a 192.168.42.X IP address on the interface of the 1941 that connects to your LAN, but use the ‘secondary’ option. This means the router will have both a 192.168.65.X address and a 192.168.42.X address.

You should then be able to PING the PBX from the router.

You will need to configure either a route or default gateway on the PBX of the 192.168.42.X address you have setup on the router to allow it to route packets between the data and voice networks.

A better practice idea as you suggested would be to setup a new VLAN for your voice network. You would need to create a trunk link from the switch to your routers inside interface then configure a sub-interface on the router for both VLANs.

Hope that helps