nanog mailing list archives

Re: It's Ars Tech's turn to bang the IPv4 exhaustion drum


From: Iljitsch van Beijnum <iljitsch () muada com>
Date: Wed, 20 Aug 2008 10:47:39 +0200

On 19 aug 2008, at 22:29, Kevin Loch wrote:

I thought there was an issue with duplicate address detection with / 127
(RFC3627)?

Don't know about that, but the all-zeroes address is supposed to be the all-routers anycast address. Cisco doesn't implement this, so /127 works on those, but there are some other vendors that do, so /127 won't work on those boxes. (And wouldn't it be funny if Cisco decided to start implementing the all-routers anycast address...)

/126 should work and lots of folks use /112 which is a more
human-friendly bit boundary.  /112 is also good for multiple access
vlans and just about anything that isn't using autoconfig.

I like using EUI-64 addressing, i.e.:

!
interface vlan666
 ipv6 address 2002:dead:beaf:666::/64 eui-64
!

This has the advantage that you don't have to explicitly assign an address to each router, it all works out automatically and you can copy/paste configs from one box to the other.

I also like to put the VLAN ID in bits 48 - 63. This makes the IPv6 addressing plan REALLY simple...


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