I need to implement VoIp service on an enterprise network.
The main campus site have two buildings. Each building has layer 2 switches on access layer and a pair of layer 3 switches on the distribution layer. Intervlan routing on each bulding is done by the distribution switches.
On the core layer i have a pair of layer 3 switches connected (l3 links) to each pair of distribution switches on the buildings.
Two routers are connected to the core switches, these routers access to the Corporate WAN.Alsa there is firewall connected to core switches for Internet access.
The main campus has 380 workstations and require 100 VoIP phones. Main site is connected over the private WAN to 20 branch offices.
Each branch office has an average of 40 workstations and require 20 VoIp phones.
I need VoIp calls among Main site and branch offices and also PSTN connection so I should implement a Voice Gateway.
Based on the quantity of VoiP phones required I suppose I can use the Call Manager Express function included on the Cisco Routers. in both: main site and branch offices for managing VoiP calls and also use the routers for connection to PSTN I have the next questions:
1- In case of the main site, can i use one of the two WAN routers like Voice Gateway or i should get other router like dedicated voice gateway and stay with the two roures for the WAN? what is the best practice? I fear if i use one of the two WAN routers, this router will increase its workload and will affect the WAN data network performance
2- same number 1 question but for branch offices. Each branch office has just a router connected to core/distribution switches (collapsed network model)
3- In case i should use a router like dedicated voice gateway, where should be connected this router? to access switches? to distribution switches or to core switches like the WAN routers?
Thanks in advance for your help
