Using /126 for IPv6 router links
gdt at gdt.id.au
Mon Jan 25 00:42:04 UTC 2010
On 24/01/10 12:54, Owen DeLong wrote:
> Use the /64... It's OK... IPv6 was designed with that in mind.
I'd suggest using a /126. For two reasons.
1) Using EUI-64 addresses on router-router links is an error, the
consequences of which you encounter the first time you replace
some faulty hardware. I have made this error :-( If you
are not using EUI-64 then assigning a non-autoconf /64 is no
less or more work than assigning a non-autoconf /126.
2) Having a block of addresses for router-router links (and other blocks
for other infrastructure such as loopbacks and unicast) makes ACLs
much simpler. Using a /126 means that this block can last for a long,
long time, reducing configuration maintenance.
 Basically, interface addresses end up scattered through the
router's configuration (some manufacturers are better than
others in this regard). Tracking down all the references to
an address and changing the config merely as the result of a
hardware swap is painful and adds complexity at a time when
it is not desired.
Glen Turner <http://www.gdt.id.au/~gdt/>
Australia's Academic & Research Network <http://www.aarnet.edu.au/>
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