[Udpcast] (no subject)

Matthew Richardson Matthew.Richardson at ee.ed.ac.uk
Tue Feb 4 10:10:56 CET 2003

> Our router equipment allows for multicast, however the
> broadcast discovery packets are killed.  So, it seems
> that I'm not able to image a machine on say
> 192.168.6.X subnet from 192.168.7.X subnet.
> Am I just missing an option, or is it possible to
> specify an IP address that the clients can listen to,
> or possibly a way to specify a list of IPs to include
> in the multicast offer?

I've been trying to get Multicasting to work in my department across
subnets, and so far to no avail.  The full list of options at:


Suggests the use of TTL, along with mcast-all-addr (control address) and
mcast-addr (data address).

"By default mcast-all-addr is the Ethernet broadcast address if ttl is 1,
and otherwise"

Note that mcast-all-addr must be set on both sender and receiver.

However, I haven't been able to get this to work - I've been assured that
multicasting is switched on on our router, but I haven't tried packet
sniffing or extending the ttl as well - if anyone else has this working
can they post a 'howto'?

> O.K.  I'm on a roll here today.  One more question.
> I'm looking at creating a FreeBSD utility CD that
> includes the udpcast program.

We've been using a linux boot disk here to get machines built - basically
it boots into linux (using Syslinux), then loads networking and gets
everything else it needs into a local ramdisk (IDE drivers, applications
etc)  We've used a combination of dd.gz, parted and udp-sender to
multicast an image to several machines and resize thir partitions (note
you can use tee and named pipes with udp-sender so that is multicasts the
image and writes to its own hard drive - meaning you can use a lab machine
as the sender, getting round the subnet multicast issue.  We're still at
the development stage, but it all seems to be working well.

Good to know there are other people out there using this great tool.


Matthew Richardson
School of Engineering and Electronics,
The University of Edinburgh, King's Buildings,
Mayfield Rd, Edinburgh EH9 3JL
M.Richardson at ed.ac.uk

More information about the Udpcast mailing list