[137072] in North American Network Operators' Group
Re: IPv6 addressing for core network
daemon@ATHENA.MIT.EDU (Iljitsch van Beijnum)
Wed Feb 9 04:15:22 2011
From: Iljitsch van Beijnum <iljitsch@muada.com>
In-Reply-To: <AANLkTinohamAfAvS1bfoEStsYYDqr7bCaGSJ3-d0beUU@mail.gmail.com>
Date: Wed, 9 Feb 2011 10:15:12 +0100
To: Vikas Sharma <vikassharmas@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 9 feb 2011, at 5:24, Vikas Sharma wrote:
> I am looking for the recommendation for core interfaces IP addressing =
schema
> for Ipv6. Some different views are (PE- P - PE, point to point link) =
as
> below -
Is there a NANOG FAQ we can add this to?
> 1- Use Public Ipv6 with /122 and do not advertise to Internet
> 2- Use Public Ipv6 with /127 and do not advertise to Internet
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.
I recommend /112 because that way the part of the address after the last =
colon is the subnet.
> 3- Use Unique local ipv6 address
Not recommended, because now traceroute replies and, if applicable, much =
worse, PMTUD responses come from bogon space so some people will filter =
them. So absolutely do not do this if you have any non-1500-byte MTUs in =
your network.
> 4- Use Public Ipv6 with /64
/64 has the advantage that you can use EUI-64 addressing so you don't =
have to remember which exact address each router has, just let that be =
filled in from the MAC address. The IPv6 addressing architecture RFCs =
also say you must use /64 but no reason for this is given so I don't =
feel bound by that.
But having a global scope address on your router-to-router interfaces is =
such IPv4 thinking. You don't need that with IPv6 unless you want to be =
able to ping individual interfaces. Routing protocols only use the link =
local addresses and when ICMP messages have to be generated a global =
scope address is borrowed from another interface, such as the loopback =
interface.=
