Re: 239.255.255.250

[Joe <joe () BLARG NET>]

On Sun, 6 May 2001, George wrote:

> Running Windows ME or Whistler/Windows XP I have noticed that upon bootup I
> see packets addressed to 239.255.255.250 port 1900. Upon investigating this
> I find that this is some sort of multicast or broadcast network address
> that's meant for UPnP devices but for some reason if you are connected to
> the internet these packets are routed out to the internet (the local 224
> route does not cover them).
>
> I've posted more information about this at
> http://www.nthelp.com/upnpscrewup.htm and was wondering if anyone here can
> explain to me what this is all about? I believe it has something to do with
> IPP, UPnP, and SSDP but I don't understand what any of this has to do with
> the general internet which is where the packets are headed.

It's not headed out onto the internet - the 224.0.0.0/8 block is unroutable,
similar to the more familiar reserved IP space 192.168.(I forget) and
10.0.0.0/8.

Although the broadcast you're seeing is heading "out" on your WAN interface,
if your ISP is up-to-snuff the packets are being dropped at your gateway, as
there is (or should be) no route to that block. (Assuming of course, there
is no multicast service running on or available via the gateway). Even if
you're ISPs routers let it through, there are no routes on the backbones
that can take it anywhere, so the "public internet" is never going to see
those packets.

So what you have is some service or device on your machine wanting to use
multicast for something (or maybe just checking to see if any multicast
services are available) - no harm no foul, and certainly not a bug.

--
Joe                                     Technical Support
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