Dial-Peers

Its that time. dial-Peers are one of the most important parts of your VOIP network.

2 types of Dial Peers

POTS- THey usually point to the PSTN or a FXO/FXS port.

Voice- These can point to a call manager, Gatekeeper, another voice gateway.



In most networks your going to have at least a few call legs and you are going to have dial peers on each of those legs. As an example.

Now the key part is that there has to be something that matches when it comes to inbound and outbound dial-peers and it can get a little tricky with the logic on how inbound and outbound dial-peers work.

Inbound dial-peer:

When you get a call from the PSTN from a ISDN line or a FXO port there is going to be a dial-peer that it matches. Its usually going to look something like


dial-peer voice 1 pots
incoming called-number .
direct-inward-dial
port 0/0/0:23

We have the dial-peer the number(tag) can be anything and we have it as a pots dial peer. The next part we have incoming call number with a "." to match anything. We have direct-inward-dial so we don't get another dial tone(i'll get to that in part 2) and we have the port that it comes in on. So when the call comes we are matching anything so it doesn't have to go down the list of options. If we didn't it would match:


1. Called Number/DNIS Incoming called-number(command)which we are using

2. Calling number/ANI Answer-Address(command) we can use this kinda like a route map where we can have "policy based calling"

3. Calling number with Destination-Pattern command

4. Voice port (bad choice)

5. Default dial-peer 0 (even worse choice)


So once thats taken care of we have matched the 1st call leg. Now we need a outbound dial-peer to send the call on its way.


So an outbound dial-peer will look something like:

dial-peer voice 2 voip
destination-pattern [347]..
session target ipv4:192.168.100.10

So the outbound portion is not as complex as the inbound. As you can see we have a voip dial-peer a destination-pattern where we are looking for a 3,4, or 7 and any other 3 digits and we the session target ipv4 command pointing to another IP address which can be another router, call manager and so on. If we are sending the call to call manager, call manager will start its process of routing the call, to the correct endpoint and if we are going to another router we are starting this process all over again until we reach our destination. This is a pretty high level overview. I didn't touch of overlapping digits, DID, and a few other commands you can add onto dial-peers to get more control out of them. Look for that in an upcoming topic.