On 23/01/2010, at 1:31 PM, Jay Nugent wrote: > Greetings, > > On Fri, 22 Jan 2010, Seth Mattinen wrote: > >> In the past I've always used /30's for PTP connection subnets out of old >> habit (i.e. Ethernet that won't take unnumbered) but now I'm considering >> switching to /31's in order to stretch my IPv4 space further. Has anyone >> else does this? Good? Bad? Based on the bit of testing I've done this >> shouldn't be a problem since it's only between routers. > > Yes, this *IS* done *ALL* the time. P-t-P means that there are ONLY > two devices on the wire - hence point to point. It ONLY uses two IP > addresses (one on each end) and there is no reason or need to ARP on this > wire. So no need for a broadcast or network addresses - it is just the > two end points.
ARP is still required on ethernet links, so that the MAC address can be discovered for use in the ethernet frame header. /31 does not change the behavior of ARP at all. -- Nathan Ward