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New Member

Remote VoIP users

We are looking for a solution for remote users (telecommuters) to have "internal" phone numbers. We have CallManagers and Cisco IP Phones in the office. Also we're piloting a "telecommuting project", where users work from home through VPN. Currently we are trying Cisco SoftPhone and Cisco IP Communicator, but it's software solution, and we need to have VPN set up before user can start make/receive a call.

Our goal is to utilize an ATA adapter (Cisco or non-Cisco), to provide office phone numbers to users' home. We're thinking to put a CallManager (probably CCM 5.0 because of SIP support) in the DMZ, and have SIP Fix-up configured on our PIX firewall. Is it better to to make this CallManager a Subscriber, or make it a separate cluster with a trunk to "inside" CallManagers?


Re: Remote VoIP users

Yes, you could do it with ATA adapters (Cisco, Sipura, Linksys, Grandstream) or IP phones.

IMHO, it would be better to put the SIP-dedicated CCM (or you can use any other SIP proxy - SER, Asterisk, Communigate Pro and etc) as a separate server and trunk it to the inside Call Managers.

Configuring the SIP-dedicated CCM as a Subscriber will merely let you open more ports at the PIX firewall and will add CPU and bandwidth overhead.

Just my personal opinion.

New Member

Re: Remote VoIP users

What'd be easier and "cleaner" - get SIP gateway (CCM5.0 or Asterisk) in the DMZ, trunking to the "Inside CCM cluster", or get Cisco router, working as SIP gateway? My concern is RTP (or even SRTP) stream through the PIX firewall. I see a couple options:

1. CCM5.0 in the DMZ, connected by the SIP trunk to the Corporate CallManager Cluster. When user calls, DMZ CCM establishes the SIP session, and then RTP/SRTP stream goes through PIX directly to endpoint.

2. CCM5.0 in the DMZ has MTPs, and works as RTP proxy for remote users (is it possible)?

3. Cisco router in DMZ terminates SIP and RTP, and brings calls inside through T1 trunk.

4. Get Asterisk at DMZ to do any of previous 3 scenarios.

Are these solutions feasible? Which one is more prefered?