[Asterisk-Users] Re: host=dynamic and defaultip=xxx

[Stephen R. Besch]

Philipp von Klitzing wrote:
> Hi there,
> 
> can anyone shed some light about the use of
> 
> "host=dynamic" and
> "defaultip=xxx.xxx.xxx.xxx"
> 
Experimentation with host=dynamic revealed that it means that asterisk 
will create an entry which waits for the remote end to register (i.e. 
call up and pass the remote IP address to *). It is essential if the 
remote unit is using DHCP or some other means to dynamically get it's IP 
address. It can also be used when the remote IP is fixed. In this case, 
when the remote end registers, it will send its IP address to *. If you 
have a fixed IP, then you can also enter it as host=ip and avoid 
registration/re-registeration issues altogether. In this case, instead 
of a formal registration procedure, * will send a query packet every so 
often (qualify=xxx, in ms) to see if the IP is available, and if it is, 
it will use the IP. Apparently, it will accept packets from the address 
in any case.  This can be useful in cases with hardware that has 
re-registration issues (such as the Grandstream phones - but this may 
have been fixed). If you have a very large installation, the dynamic 
option is really useful, since it frees you from having to enter and 
maintain all of those IP addresses in the configuration files. In a 
small installation, it is probably better to use the host=IP option, 
since it should have a higher reliability in terms of availability

 From what I can tell, the defaultip is used to define the address of a 
remote device (phone, etc) which is to be rung if the device specified 
in the host= option is, for some reason, unavailable.  The idea is to 
pass incoming calls over to some predefined, reliable, unit when the 
dialed one is off line. I have no experience with its use in iax.conf.