Archived from groups: comp.dcom.voice-over-ip (
More info?)
"Rick Merrill" <jaynehm@comcast.net> wrote in message
news:Na-dndufj8vtiAzfRVn-pg@comcast.com...
> Wolfgang Barth wrote:
> > Rick Merrill wrote:
> >
> >>
> >> Your configuration should look like this:
> >> Modem<==>SPA3000<==>Router<==>pc(s)
> >
> > But I have a modem-router with DHCP and behind that there is
> > the SPA3000 and the PCs. I cannot change this configuration.
>
> Why not? How do you expect the SPA3000 to do QoS?
For example, because the router handles the PPPoE decoding and NATting.
> >> and all four devices should use DHCP to get IP and DNS addresses.
> >
> > PCs and Sipura do use DHCP to get local IP and DNS addresses.
> > The modem-router gets its via PPPoE.
>
> Why is that?
Because that's how things work when your provider uses PPPoE and gives
you only one IP address (assigned through PPPoE), which obviously can't
be shared among devices: hence the need for NAT functionality, and
often the DHCP service to assign the local IP addresses, both of which
can be provided by the route.
That said, I have the same configuration as Wolfgang's (SPA-3000 behind
the NAT router) and never noticed that problem. On the other hand, I
used to have a different type of problem with a Netgear MR814v2
(http://voxilla.com/index.php?name=PNphpBB2&file=viewtopic&p=13986#13986
). Now I'm running Linux on a Linksys WRT54G (http://openwrt.org ) and
Netgear is only a painful memory
The nice thing of using Linux as router is that one can run tcpdump to
capture packets to a file, transfer the file to a bigger machine and
inspect them with Ethereal. This would tell you more about why the
re-registration fails: which is a quite unusual thing. Wolfgang, are
you sure it fails? Or perhaps is it not repeated often enough, so that
after the change of IP address the remote SIP registrar still remembers
the old address? In that case, you could try to reduce the
re-registration interval of the SPA-3000 to, say, a couple of minutes.
You can do this putting 60 (the number of seconds) in the "Register
Expires:" field of the "Line 1" and "PSTN Line" screens of the Admin
interface.
Another way of inspecting the SIP packets would be installing a NON
switching 10baseT hub between router and SPA-3000, and use it just like
a T-joint to tap into the traffic with a monitoring machine directly
running Ethereal. Unfortunately, in these days non-switching hubs are
hard to find.
Enzo