Confused by DUNDi? Yeah, so was I. It took me a few weeks of kicking my Asterisk box, but I finally got it working. Here’s a step by step tutorial on how to get DUNDi working with Asterisk@Home. This tutorial was written using an Asterisk@Home 2.5 system with FreePBX 2.1, but should work from Asterisk@Home 2.0 onward.

First, let’s be clear about what the end goal of this setup is.

Nerd speak: The end goal is to connect two or more Asterisk@Home systems using Mark Spencer’s DUNDi protocols so that every system on the network esentially has the same dialing abilities. That is, if system A has the ability to dial the 416-238-XXXX exchange locally, then so would all the other connected systems, even if they’re nowhere near that particular exchange. This setup also enables each system to call the extensions on other connected systems. Both of these things are accomplished without any particular node on the network being statically programmed with routes to access the features on any other node.

Layman’s terms: Free long distance. If you have a friend in New York City, and you live in Toronto, you could use his phones lines, and he could use yours. You don’t have to dial any special access codes or PINS, it just happens transparently in the background.

Caching

Before we start, it’s important to know that DUNDi caches routes for one hour by default. This means that if you make a mistake in your configuration, you need to clear your cache before accurate routes will be returned. At the Asterisk CLI, type dundi flush to clear the cache.

Ports

Note that DUNDi uses UDP port 4520 to communicate between servers. If you’ve got a firewall on your boxes, open that up.

Configuration Files

On BOTH boxes, add the following to the appropriate config files:

[priv]
type=user
dbsecret=dundi/secret
context=dundi-priv-local

iax_custom.conf

[general]
; Define the max depth in which to search the DUNDi system (also max # of
; seconds to wait for a reply)
;
ttl=32
; If we don’t get ACK to our DPREQUEST within 2000ms, and autokill is set
; to yes, then we cancel the whole thing (that’s enough time for one
; retransmission only). This is used to keep things from stalling for a long
; time for a host that is not available, but would be ill advised for bad
; connections. In addition to ‘yes’ or ‘no’ you can also specify a number
; of milliseconds. See ‘qualify’ for individual peers to turn on for just
; a specific peer.
;
autokill=yes
; If the cache time is too large, a route may change and be unreachable
; until the cache expires. By contrast, if you have a large network, it is
; extremely inefficient to be sending every single search out to the network
; simply because one’s cache expires after a few seconds. Try to adjust
; this based upon the size of your network. By default this is set to
; 3600 seconds (one hour). This will work fine for a fairly static setup,
; but should be lowered for a more dynamic environment.
cachetime=3600
[mappings]
priv => dundi-priv-canonical,0,IAX,priv:${SECRET}@${IPADDR}/${NUMBER},nopartial
priv => dundi-priv-customers,100,IAX,priv:${SECRET}@${IPADDR}/${NUMBER},nopartial
priv => dundi-priv-via-pstn,400,IAX,priv:${SECRET}@${IPADDR}/${NUMBER},nopartial

dundi.conf

Important: During some testing, it’s come to my attention that the ${IPADDR} variable may report 127.0.0.1 instead of your actual IP address. I have specified my hostname in place of ${IPADDR}, you may wish to do the same, or use your IP address (if it is a static IP). Thanks to Elliot Spencer for pointing this out!

; Private DUNDi network
[dundi-priv-canonical]
; Direct numbers

[dundi-priv-customers]
; If you are an ITSP or Reseller, list your customers here.

[dundi-priv-via-pstn]
; If you are freely delivering calls to the PSTN, list them here
[dundi-priv-local]
include => dundi-priv-canonical
include => dundi-priv-customers
include => dundi-priv-via-pstn

[dundi-priv-switch]
; Just a wrapper for the switch
switch => DUNDi/priv

[dundi-priv-lookup]
include => dundi-priv-local
include => dundi-priv-switch

[macro-dundi-priv]
exten => s,1,Goto(${ARG1},1)
include => dundi-priv-lookup

[trydundi]
exten => _.,1,Macro(dundi-priv,${EXTEN})
exten => _.,2,Congestion

extensions_custom.conf

Keys

This is the toughest part of this particular setup… But only because you can’t copy and paste! On each box in the DUNDi cloud you must complete the following procedure. Note that SERVERNAME is the hostname of the box you are currently creating a key for. If you can use a fully qualified hostname, you’re better off doing so to avoid confusion between keys in larger networks (ie. If you have a server bob on the domain domain.com, you should use “astgenkey -n bob.domain.com” instead of just “astgenkey -n bob”).

1. cd /var/lib/asterisk/keys
2. astgenkey -n SERVERNAME

You should see two new files created: SERVERNAME.key and SERVERNAME.pub. You need to find a way to copy your public (.pub) keys between all servers in your DUNDi cloud. If you have a web server, put them up there for easy downloading. Otherwise, remember that they key is just text, and you can copy and paste the key’s contents so long as you name it correctly on the receiving server.

Entity ID / Media Access Control

Now that you’ve got all the public keys from all the servers in your cloud copied on to every other server in the cloud, you need to tell each server how each box will identify itself, and which key to associate with each identity. DUNDi uses an Entity ID (EID) number, also known as a Media Access Control (MAC) address, to identify servers within the cloud. DUNDi defaults to using the MAC of eth0. As such, there are two ways to obtain the EID/MAC for each server.

One: At the shell, enter ifconfig eth0. You should see output similar to the following:

[root@pbx ~]# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:02:A5:AA:08:72
inet addr:192.168.0.1 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::202:a5ff:feaa:872/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:110179799 errors:0 dropped:0 overruns:2 frame:2
TX packets:110153248 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:3265363193 (3.0 GiB) TX bytes:2060951955 (1.9 GiB)

Note the bolded section. This is the MAC address.

Or, two: At the Asterisk CLI, enter dundi show entityid. You should see output similar to the following:

pbx*CLI> dundi show entityid
Global EID for this system is ‘00:02:a5:aa:08:72‘

Pretty self explainatory, but the bolded text is the EID. Note how the two commands identified the same ID when used on the same server. Make a note of the EID/MAC for each server, as you will need it finalize your dundi.conf file.

Final dundi.conf Configuration

For clarity in this section, I’ll be pretending I have two servers: pheonix.thegoldfish.net and unlimited.thegoldfish.net. Their keys have been generated as pheonix.thegoldfish.net.key/pheonix.thegoldfish.net.pub and unlimited.thegoldfish.net.key/unlimited.thegoldfish.net.pub, respectively.

In the dundi.conf on pheonix.thegoldfish.net:

[00:14:2a:30:71:a4] ;unlimited.thegoldfish.net EID
model = symmetric
host = unlimited.thegoldfish.net
inkey = unlimited.thegoldfish.net ;Unlimited’s public key
outkey = pheonix.thegoldfish.net ;Pheonix’s private key
include = priv
permit = priv
qualify = yes
order = primary

In the dundi.conf on unlimited.thegoldfish.net:

[00:02:a5:aa:08:72] ;pheonix.thegoldfish.net EID
model = symmetric
host = pheonix.thegoldfish.net
inkey = pheonix.thegoldfish.net ;Pheonix’s public key
outkey = unlimited.thegoldfish.net ;Unlimited’s private key
include = priv
permit = priv
qualify = yes
order = primary

DUNDi Trunk

To create a trunk that you can use to check if a number is available anywhere within your DUNDi cloud, complete the following steps in FreePBX:

1. Click on Setup in the menu in the top right-hand corner of the page.
2. Click on Trunks in the menu on the left.
3. Click on Add Custom Trunk.
4. Fill out your outgoing caller ID to identify yourself.
5. Fill in your dial rules as appropriate. I have set mine to strip out the 1 passed to the trunk for long distance calls. If users dial extra digits to get an outside line, you may wish to strip those digits out here.
6. For custom dial string enter the following: local/$OUTNUM$@trydundi
7. Save the trunk.

You now have a trunk that you can use to check if an alternate route exists for placing a call before it is routed using your standard means. For example, I have setup an outbound route for my long distance calls. The call is first passed to my DUNDi trunk. If no route is found, the call is routed using my ITSP.

So now you can use the DUNDi cloud to make calls. There’s just one last step to make your node a full fledged member of the cloud.

Advertising Routes

A DUNDi network only works if everyone shares their resources as well as consumes them. If you’re in my cloud and you’re not sharing routes, you’re cut immediately. To this end, you must advertise which calls you are willing to terminate. In my case, I simply asked my ITSP for a list of exchanges that were local for me to call, and advertised all of them. That way, anyone who needs to make a call that is local to me can do so at no charge to either of us. Here’s how you advertise routes:A route is simply advertised as if it were normal extension. For example, if I wanted to terminate calls to the 289-242 exchange, I would add this to the [dundi-priv-via-pstn] context in my extensions_custom.conf file:

exten => _!289242XXXX,1,Dial(SIP/Iristel/${EXTEN})

Where SIP/Iristel is my ITSP trunk. Iristel is the name I gave the trunk in FreePBX, so simply use the name you’ve defined for the trunk there. It’s also a good idea to advertise any numbers that you own. In this case, add the following to the [dundi-priv-canoical] context in extensions_custom.conf file:

exten => 4162382936,1,Goto(from-pstn,s,1)

Where 4162382936 is my DID. This sends the call straight into my [from-pstn] context, just as if it were a standard incoming call.

If your goal is to make extensions on one server accessible on another, add lines similar to the following in the [dundi-priv-customers] context in extensions_custom.conf:

exten => _2XX,1,Goto(ext-local,${EXTEN},1)

In this case, we would be advertising that any three digit extension starting with a “2″ is available on this box. This is very dependent on how you split extensions between your boxes. You may need to define this more clearly, such as “2[2-9]X” for extensions 220 through 299 for example.

That’s All She Wrote

Good luck! Thanks to Elliot Spencer for his help with this, and the forum members of FreePBX who gave me a kick in the right direction.