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Cisco Voip for SIP line


Can anyone please share their experience with Cisco voip for Sip line.  

Need to provide the Cisco Voip solution for 3 location 

  1. Main office – 152 Connections
  2. Site Office 1 – 128 Connections
  3.  Site Office 2 – 70 Connections.

 SIP Line from service provider terminated at Main office consisting of 20 DID/20 DOD with 400 extensions

9 Replies 9

Mohammed al Baqari
VIP Advisor VIP Advisor
VIP Advisor


This is a design question which requires lot of information to be gathered and collaboration experience. From my experience, I can suggest couple of points:

1. What kind of buisness is running and how phone dependent it is? This is important to define the SLA which will be a base line for aspects of design

2. You need to think about WAN Topology and bandwidth such full-mesh MPLS, DMVPN, or combo

3. Think about Grade of Service and whether to use Erlang B/Erlang C (for contact center enviroment) for your concurrent call calculations

4. Codec to be used for intra-call and inter-call. This is important for bandwidth calculation

5. QoS for LAN and WAN and which model to use with how many CoS

6. Deployment Model (centralized or Distributed)

7. Redundancy level (How many Sub, Local Failover or Remote Failover, SRST)

8. Router Platform to use and Amount of DSPs (Cisco Online DSP Calculator can help)

9. Which signaling protocol to use in case of multi-cluster

10. Dialplan and Numbering. Advanced Call Routing such as ILS/GDR, TEHO, etc

11. Is video calling an option

12. What endpoints are required

13. Other options such as voice mail and IM

14. CUBE Design since you are connecting to ITSP using SIP (Number of concurrent calls, HA, etc)


Can I use cisco business edition 6000S for each location or cisco business edition 6000M as centralized for 3 locations together?

B6KS can have max of 150 users. Therefore main office can't use it. Also, I don't recommended it for site 1 (128 is very close to 150 and you need a space for upgrade).

If you want to go for centralized deployment you can go for B6KM which can have up to 1000 users which is more than double of you total count. Also, B6KM can support more options as such UCCX users, CUC, etc


So if I go for centralized at main site, then for site 1 & 2, what would I require in addition to  layer 3 switches 3850 for routing and poe. Will the main site CBe 6000M be sufficient?

Also since the ITSP is terminating SIP trunk at main office. Do I require anything additional to be added like cube?

Will the main site CBe 6000M be sufficient?

Yes but you need to consider HA options such as SRST license on local routers.

Do I require anything additional to be added like cube?

Yes you need a CUBE to integrate with telco. Technically, you can connect CUCM directly to telco but this isn't not a right design at all.

Could you please suggest a good link from which I can gather more about this scenario? This is first time for me so not very sure about the solution.

Will it be a bad choice to go for CBE6000M for main and CBE6000S for each smaller sites as design?

Can C3925E-CME-SRST/K9 be used as call manager for 350 users as centralized deployment in main office and on sites 2951 SRST or is BE6000M required in main office with C3925E-CME-SRST/K9 seperately?

Please use this link. It will give you the details about possible deployments model.

CUCM SRND have all the details about CUCM design

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