When using Kamailio with the dispatcher module for Asterisk load balancing, I am offloading REGISTERs to Kamailio (works fine), but would like to forward the REGISTERs to Asterisk so that outgoing calls from Asterisk will be possible. I know this is not strictly necessary (e.g., just use Kamailio to forward everything), but I have a lot of application logic behind my Asterisk boxes (using ARI) and so I don't want that to break. Thereby, I do need this information in Asterisk as soon as possible from Kamailio.

Let's say I have three boxes Asterisk_1, Asterisk_2 and Asterisk_3 in the dispatcher module like so:

My system has endpoints as numerical extensions, from 101 to 110. When a new endpoint registers with kamailio (and authenticates), I would like to send the REGISTER to Asterisk. But I have the following questions:

(a) Which Asterisk? I could send it to a round-robinned Asterisk (say, Asterisk_2), but that Asterisk may not be the one responsible for handling calls outbound for the endpoint that just registered. Even if I use "hash over auth username" instead of round-robin (In http://www.kamailio.org/docs/modules/4.0.x/modules/dispatcher.html#idp16940048, choose 5 for "alg", for example) that wont solve this problem as an outbound request may come from another Asterisk box which won't have the requisite registration information. Should I forward REGISTERs to all Asterisk boxes? Maybe I won't have to deal with this issue as I use realtime and so the REGISTER information, sent to one Asterisk box, is available to all Asterisk boxes after the write to the realtime DB. Is my understanding correct?

(b) How do I do this in kamailio.cfg? With some examples on the Internet for WITH_ASTERISK directive, I see that you do 

What is the equivalent for when you are using the dispatcher module and the kamailio.bindip and asterisk.bindip etc. are not set in the configuration, but instead should be procured from elsewhere?

Any help is appreciated.