[afripv6-discuss] IPv6 netmask on multi-access network segments

Warwick Duncan warwick at frogfoot.com
Fri Feb 7 19:38:12 SAST 2014


I've been following
http://bcop.nanog.org/images/6/62/BCOP-IPv6_Subnetting.pdf for IPv6
subnetting, which makes the following two points:
- each network segment should be allocated a /64;
- point-to-point networks should be configured as /126.

So simply speaking, the IPv6 equivalent of an IPv4 /30 is a /126, even
though it does actually 'own' a /64.  But what about the IPv6 equivalent
of an IPv4 /29 or /28, where one might have multiple routers in a full
mesh without the bother of configuring multiple /30's?

I've chosen to configure these as /120 because a) that's surely big
enough for any router-router interconnect network and b) it's
nibble-aligned.  I guess also c) it seemed like a good idea at the time.

Is this a bad idea for any reason?  Is there a best-practices document
I've missed or someone's practical experience that suggests some more
suitable netmask for this sort of link?


Warwick Duncan
Frogfoot Networks ISP

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