[154917] in North American Network Operators' Group
Re: using "reserved" IPv6 space
daemon@ATHENA.MIT.EDU (Owen DeLong)
Tue Jul 17 00:16:39 2012
From: Owen DeLong <owen@delong.com>
In-Reply-To: <2059648.BTFFAkdkz4@lsdsrv>
Date: Mon, 16 Jul 2012 21:11:18 -0700
To: Oliver <olipro@8.c.9.b.0.7.4.0.1.0.0.2.ip6.arpa>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Jul 16, 2012, at 12:39 PM, Oliver wrote:
> On Monday 16 July 2012 18:26:08 Rajendra Chayapathi wrote:
>> On the HSRP/ND part , this all falls in the First Hop redundancy =
areana
>> and can be achieved via any of the following and each has its merits =
and
>> cons..
>>=20
>> 1) Using ND -- need to tune the "IPv6 nd reachable time" to achieve =
the
>> faster failover
>> 2) Using any of the First hop redundancy protocol ( HSRP, VRRP , =
GLBP)
>> 3) Default route selection.
>>=20
>=20
> In all honesty, I think using ND as the failover method is a generally =
bad=20
> idea - you have no way of ensuring all endpoints take note of or =
honour the=20
> router preference flag.
Huh? Any host which doesn't is provably buggy. I'm not saying it can't =
or won't
happen, but, seriously? If the host is that buggy, you can't count on it =
using
the fake MAC either.
> Additionally, having a 1 second validity lifetime is going to create a =
lot of=20
> ICMPv6 spam across the segment - big deal? perhaps not. But when =
contrasted=20
> with the fact that it can be wholly avoided using one of the =
aforementioned=20
> redundancy protocols, why would you do it?
You don't need a 1 second valid timer (that would be absurd). You need a
1 second keep alive (if you really care about 1 second fast fall-over) =
and you're
going to get just as much SPAM with sub-second fallover from any of the =
other
solutions as well. They all send multicast packets.
> Additionally, as an alternative to RAs, you can simply point default =
at the=20
> all-routers anycast address.
The disadvantage to this is the high probability of packet duplication. =
For
someone worried about ICMP spam on the subnet, I'm surprised you're not
worried about what happens when 2 or more routers copy the same packet
and route both copies on to the end destination. (Lather, rinse, repeat =
said
duplication for any upstream segments using such tactics as well).
Owen
