[NTLUG:Discuss] Broadcast IP address

[Leroy Tennison]

On 11/09/2012 04:42 PM, Ralph Green wrote:
> Howdy,
>    I have a network I want to expand a bit with as little impact on the
> users as possible.  All LAN addresses are currently in the 192.168.4.x
> range.  I am adding a new VPN server and I am thinking of using
> 192.168.5.1 for its address.  It looks like I need to adjust the
> netmask on machines in the original LAN from 255.255.255.0 to
> 255.255.254.0.  If I do that on a test machine, I can reach it from
> the 192.168.5.x machines.  I see the broadcast address has changed
> from 192.168.4.255 to 192.168.5.255.  If I make the netmask change on
> the servers, including the DHCP server, will clients be able to renew
> their leases?  I am thinking they will broadcast on 192.168.4.255 to
> get a renewal and they won't find a response.  What would be a good
> way to resolve this?  The only thing I can think of offhand, is maybe
> to add a new machine temporarily at 192.168.4.255 and forward packets
> to 192.168.5.255, but I think that might be a bad IP address for a
> machine on the network.
> Do you have any suggestions,
> Ralph
>
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Where is the DHCP server?  If it's on the same subnet then it should see 
the broadcast of the clients.  The real question is what happens when 
they try to renew their lease?  It shouldn't be granted because the 
subnet has changed.  What I would hope would happen then is the client 
would request a new IP address on any subnet and be granted one on the 
new subnet.  This is the way Windows works but I've never had the need 
to find out what happens on Linux.