Eric Sisler wrote:
> Maybe I should say "sort of" solved in that it works but I don't understand
> why.
Because DHCP requests and ack's are broadcast. The IP's don't make any
difference.
> The problem wasn't dhcpd or the dhcpd.conf file. We took another
> look at the old server and the subnet mask the "real" device (eth0) was
> correct for a class B network subnetted to class C (255.255.255.0).
> However, the aliased IP device (eth0:0) had the subnet mask for the class B
> (255.255.0.0). I don't understand why it works this way - can anyone shed
> some light?
If you were using a class B network, say 192.168.0.0, subnetted into
192.168.76.0 and 192.168.78.0 using the above netmasks, your routing
will still work correctly.
Traffic sent to 192.168.76.XX is broadcast to the network, because the
netmask includes that entire network. Traffice sent to 192.168.78.XX
will also be broadcast to the network, and recieved by the appropriate
machines. The problem, however, would lie in attempting to send data to
192.168.75.XX, or 192.168.15.0, or any other class C in 192.168... The
255.255.0.0 netmask may tell the kernel to broadcast these packets to
the local net, and not to a router. Unless your router does reverse arp
proxy, (and some do) then your traffic would be lost.
Now, since DHCP requests are broadcast, and do not have src/dst
addresses to speak of, routes, ip's, and netmasks don't have much
effect. Both of your subnets speak to the same physical device, so the
DHCP server will assign addresses from the same pool, unless the
ethernet address is listed in the dhcpd.conf, and given a specific IP
there. There is no other way for the DHCP server to know which subnet a
given computer is on.
Most subnetting schemes would involve two hubs (or pools of hubs) and
two NIC's in your linux box/router. In this case you'd have eth0 and
eth1, not eth0 and eth0:0. Because there are distinct physical devices,
dhcpd knows which subnet should recieve what addresses.
Sorry if my previous post was a little curt, sometimes I'm hasty with
the "Alt+Enter". If there's anything you'd like me to clarify, I'd be
happy to.
MSG
--
To unsubscribe: mail [EMAIL PROTECTED] with "unsubscribe"
as the Subject.