On Mon, Oct 08, 2007 at 05:39:59PM -0400, Bill Sommerfeld wrote: > On Mon, 2007-10-08 at 10:09 -0700, David.Comay at sun.com wrote: > > However, it's my > > understanding that requiring the netmask will mean that configuring > > guest domains using our xVM implementation will differ from that of > > vendors using similar technology. > > I'm a little surprised by this. can you expand on this or explain > further? > > I'd imagine that one very common case is that the guest domain is given > an address on the same ip subnet as the host, in which case it would be > possible to for the host to unambiguously determine the correct subnet > mask for the guest based on the host's configuration. > > But the guest can't figure this out on its own.
A Linux kernel running in a guest domain is happy to guess a netmask based on the class of the IP address assigned, so an administrator is not required to specify a netmask if that derived from the class of the address is correct. The existing tools (xm/xend, virsh) and their associated APIs do not require a netmask to be specified alongside the IP address of a network interface. So, if Solaris requires that a netmask is specified it will be different to the other common guest domain implementation. If we believe that being prepared to guess a netmask results in it being wrong more than right then it is sensible to require it. I'm inclined to believe that (which is why it was originally required), but don't have good evidence to back up the belief.
