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Cisco IP Phone & DSL high–speed Internet access

When I try to setup and use a Cisco IP Phone thru DSL Internet access at home, the Cisco IP Phone is perfectly registered with the Cisco Call Manager, but I get no audio when I try to place a call to other Cisco IP Phone at the office.

Could be that RTP is block by the DSL provider ???

Can someone help me out with this issue ????


Re: Cisco IP Phone & DSL high–speed Internet access

How are you connected at home? Do you have an 8xx router or a PIX 501? What about the central site, are blocking RTP ports?

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Re: Cisco IP Phone & DSL high–speed Internet access

Hi Guys!

I have a similar problem. I'm trying to get IP Softphone running across a VPN link to our network with the Call Manager.

I connect at 512k to my ADSL provider then use VPN Client 4.0.1 to tunnel through to a 3020 VPN Concentrator running 4.0.4a. The Softphone authenticates fine and picks up my shared line at the office but it doesn't give me 2-way conversation (the dialed party can hear me but I can't hear them)

I'd appreciate any suggestions.


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Re: Cisco IP Phone & DSL high–speed Internet access

can you ping one of those IP phones that you're having trouble hearing & get a response?

If you can connect a call, then that means that your softphone can talk to callmanager & call manager can talk to you...

If they can hear you, then your RTP stream is making it through the network to their phone, but something's happening to the stream headed your way. Maybe the IP phone network at the office doesn't know how to get to the subnet that your VPN client is on (in which case pinging one of those phones should fail, because the reply won't make it back).

if the ping fails, it's probably a routing problem somewhere -- maybe the IP Phones don't have a default gateway set in their DHCP scope, maybe the default gateway doesn't know how to get to your VPN client's IP address, or maybe there's an access list blocking outbound access from the phones at the default gateway for security...


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Re: Cisco IP Phone & DSL high–speed Internet access


I've got exactly what your looking to do working perfectly. However, it's not. easy.

First of all. Where is the CallManager located? On a Private Network space? or Public IP address?

Either way, you must understand how the call setup process works. Once the IP Phone or SoftPhone registers with a CCM, it registers with its IP address. Then, whenever that Phone wants to call another phone, it makes a direct call to the other phone.

In my scnerio, I have 5 friends. All of which have IP phones at their House behind a Linksys Router, etc... We all have private IP addressing ( 192.168.x.x).

the CCM is @ my house. I have my Linksys setup to forward the ports (tcp and udp ranges) directly to the CCM, however, after the initial registration, the IP phone at House X that needs to call House Y, makes a direct call. Since we're all registered with non-routable space on the Internet, the packets are dropped at each other's ISP.

There are severa solutions to consider to make this work. One, try and keep some sort of Security, and yet, still register with a CCM with Private IP address, and still be able to call each other's houses.

I then thought, about making a GRE tunnel between each others houses. This of course, requires us have a cisco router at each house. We create a GRE tunnel between each house, and create static routes to each others network. once we did this, it didn't matter if we had private addressing or not..



House A = 192.168.1.x

House B = 192.168.2.x

House C = 192.168.3.x

House D = 192.168.4.x

Once the GRE tunnel is up between each house, we are now able to Ping each others "private" address space and keep our IP phones connected to the CCM. works great!

If anyone likes, I've drawn out a doc on how to do this on private addressing at home.


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Re: Cisco IP Phone & DSL high–speed Internet access

Thanks for the replies everyone. The CallManager is located in private network space behind a 10. address.

Once I'm connected to the network via the VPN, I can ping my IP Desk Phone without a problem. I can make, pick up and park calls but the only problem is that the audio is one way (ie. I can be heard but can't hear the other side, whether it's an IP Phone, non-IP phone, mobile or cellular)

Stateful Firewall is turned off on the VPN client but I haven't given the IP Address Autodetection a try yet. I'll give it a try and let you know how it goes. I'd appreciate any other suggestions.

And thanks again for your help everyone!

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Re: Cisco IP Phone & DSL high–speed Internet access

Have you verified that after you VPN to the 10.x.x.x network, that no FW is blocking any ports? Especially the UDP port range, i think from 16384-32767.

could be that one side has it blocked. I have seen before also.


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Re: Cisco IP Phone & DSL high–speed Internet access

1-way audio has to do with the IP address of the phone vs the IP address of the office end of the VPN tunnel. I am using 1.1.1 on my DSL running Checkpoint for the VPN. In Call Manager, in the phone programming go to device specific configuration to key IP Address Autodetection URL:

Enter the IP address of the TFTP server. There should be a file there which will tell the Communicator the correct IP address for the CM end of the VPN tunnel. e.g. put:

http://x.x.x.x/communicatorloads/communicator/getIP.asp in the field.

I've got mine working with a bluetooth headset to the laptop, which is running wireless to my DSL then VPN to the office. I make calls just like I'm in the office. I'm not even using compression on the audio stream.

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