Re: [v6ops] DHCPv6/SLAAC Make Hosts Confusing-//RE: new draft: draft-liu-bonica-v6ops-dhcpv6-slaac-problem

Nick Hilliard <nick@inex.ie> Wed, 30 October 2013 18:15 UTC

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Date: Wed, 30 Oct 2013 18:14:58 +0000
From: Nick Hilliard <nick@inex.ie>
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To: Lorenzo Colitti <lorenzo@google.com>
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Subject: Re: [v6ops] DHCPv6/SLAAC Make Hosts Confusing-//RE: new draft: draft-liu-bonica-v6ops-dhcpv6-slaac-problem
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On 30/10/2013 13:07, Lorenzo Colitti wrote:
> Find me an medium or large enterprise deployment that doesn't have two
> routers on every LAN segment. I'll bet almost all of them do, because they
> know that if one crashes or they want to take it down for maintenance, they
> have an outage, and nobody likes outages.

no need to bet - using multiple routers on a LAN is standard procedure
where uptime matters.

The question is why would someone use RA for multiple gateway announcement
when you'll get much better operational performance from a FHRP + single
gateway address?  And why use RA for addressing when you'll get finer
grained operational host control using dhcp?  Or when you need to use dhcp
anyway in order to make your hosts do what they need to do?  Or on server
farms when most of your hosts are statically addressed and it doesn't make
sense to have multiple gateways with different addresses - and you'll get
better uptime by not using RA?

I'm not proposing to take away the option of using RAs if that's what you
want to do.  I'm only suggesting that for many situations, it makes more
sense to have a single static gateway address (optionally with multiple
routers using a FHRP if you need reliability) and that consequently the
idea of periodically announcing a selection of arbitrary gateways via RA is
operationally second rate.

Nick