Re: ping-pong phenomenon with p2p links & /127 prefixes

[sthaug@nethelp.no]

> Unless you configure two /128's pointing to the remote side, which will
> then thus not be 'on-link for neighbor discovery, the little thing
> called the subnet anycast address will make sure that a /127 ptp simply
> does not work, unless you have a platform which disables the subnet
> anycast address of course.

It would seem disabling the subnet anycast is fairly widespread, then.
I have verified the use of /127 on several hardware forwarding platforms
from Cisco and Juniper. /127 works just fine, and prevents the ping-pong.

[One concrete example where /127 works: Juniper T1600 talking to Cisco
CRS-1 on an OC-768/STM-256 link.]

Steinar Haug, Nethelp consulting, sthaug@nethelp.no