[Dnsmasq-discuss] Problems With Windows Vista

[Simon Kelley]

Jeremy M wrote:
> What will the broadcast address in the --dhcp-range configuration affect 
> if not broadcast replies?

The value of the "broadcast address" option sent to the client. This 
will eventually be installed in the client's network interface, along 
with the allocated IP address and the netmask. The broadcast address and 
netmask are optional in dhcp-range, since they are normally copied from 
the interface on the server which connects to the subnet the client is 
on. It's possible to omit them, except that the netmask has to be 
supplied when using a DHCP-relay, as dnsmasq can't determine it 
automatically.

Don't forget that when the DHCP server is broadcasting to the client, 
the client doesn't yet know its IP address, so it can't respond to the 
network-broadcast address. Hence the use of 255.255.255.255


HTH


Simon.

> 
> 
> On Sun, Jan 24, 2010 at 3:39 AM, Simon Kelley <simon at thekelleys.org.uk 
> <mailto:simon at thekelleys.org.uk>> wrote:
> 
>     Jeremy M wrote:
> 
>         You were exactly right.  The firewall was blocking outbound
>         broadcast packets on the subnet.  I'm not sure if this is
>         correct, but my config specifies:
> 
>          
>          dhcp-range=wireless,192.168.3.50,192.168.3.250,255.255.255.0,192.168.3.255,12h
> 
>         I think that's saying the broadcast address should be
>         192.168.3.255, but broadcasts attempts are actually going out on
>         255.255.255.255.
> 
> 
> 
>     255.255.255.255 is always a valid broadcast address on IP networks,
>     and the correct one to use for DHCP.
> 
>     255.255.255.255 = limited broadcast address, propogates only on one
>     network segment.
> 
>     192.168.3.255 = network broadcast address. May be routed to other
>     network segments be suitably configured routers.
> 
>     I'm glad that's fixed. Probably worth a FAQ entry!
> 
>     Cheers,
> 
>     Simon.
> 
>