On 9 feb 2011, at 10:48, sthaug@nethelp.no wrote:
The all zeros address is the all routers anycast address so on most non-Cisco routers you can't use it, ruling out /127. The top 128 addresses in any subnet are also reserved anycast addresses although they don't do much in practice. So the longest prefix length you should use is /120 and only use addresses 1 - 127.
A /127 mask is still the best way to handle real point-to-point links like SDH/SONET today, to avoid the ping-pong problem. Works fine with Cisco and Juniper, not tried with other vendors.
I know it's immature, but I can't wait for some new hire at vendor C or vendor J to reread the RFCs and implement the all routers anycast address according to spect and then see sparks fly. Like I said, global scope addresses on your router-to-router interfaces is such IPv4 thinking.