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New Member

Questions IP Telephony

Hey all,

I have limited knowledge about IP Telephony. If anyone can answer the following questions that would be great!

1. What is the IP structure used in a voice/data LAN? private or public? 10.x.x.x for data and 172.16.x.x for voice?

2. Is is standard to have physical separation or logical(VLAN) & if logical do you use acls to keep traffic from crossing.



New Member

Re: Questions IP Telephony

Hi Howard

Usually we use Data VLAN and Voice VLAN also we use private addressing for example 172.16.10.x for Data and 172.16.20.x for voice.

Sometimes routing between these two VLANs is required to use IP Telephony Clients (Softphones).

Super Bronze

Re: Questions IP Telephony

Hi Howard

1. There is no set structure for IP addressing, but since most deployments are not Internet-facing it is a standard recommendation for this and most other networks to use private addressing - within the available ranges you use whatever is appropriate for your network.

If for example you have your LANs in the 10.1.x.x range, it might make sense to use a parallel range such as 10.2.x.x for ease of recognition when troubleshooting etc..

2. Many deployments allow full routing between the subnets - however if it isn't required it makes sense to limit traffic to the Voice network in order to give further protection to your voice servers...


Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

Re: Questions IP Telephony

hi aaronharrison & awaleed.samir

thank you for the information.

it has helped me greatly.


New Member

Re: Questions IP Telephony


Take a look at the callmanager solution refferrence network design guide for deployment and design examples,It allways best to use voice and data vlans as they help you to prevent ur data traffic overwhelming the voice traffic.



New Member

Re: Questions IP Telephony

Just want to tell you that if your network is really small and you have a very small number of IP phones, then you can use the phones in the data vlan, but if your network is medium to large or, might expand in the future, please use different vlans for your ip phones and other devices on the network. This makes troubleshooting easier and there isn't any fear of collisions on the network, which will surely bring down your voice network.

So, visit the url given to you by our friend Mr. Aman Chugh and it will explain you the entire design.

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