VoIP Solution Assistance Needed

[Frederick Anim Oturoku]

Hello All,

Please i need assistance in designing a solution for the below; 

I will be using 7821 phones and want to know whether if i use a 2911 router I will be able to do the below and this solution should be capable of allowing inter-branch communication. 

1. The head office has 25 users, 4 landlines and 2 GSM's
2. Branch 1 has 5 users and 1 GSM line
3. Branch 2 has 7 users and 1 landline and 1 GSM lines
4. Branch 3 has 5 users and 1 GSM line
5. Branch 4 has 4 users and 1 landline
6. Branch 5 has 5 users and 1 GSM line