Date: Tue, 18 May 1999 23:34:07 -0600 From: Wes Peters <wes@softweyr.com> To: justin@apple.com Cc: freebsd-net@FreeBSD.ORG Subject: Re: Redirects and expire times Message-ID: <37424D4F.D9259DBA@softweyr.com> References: <199905190411.VAA00649@walker3.apple.com>
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"Justin C. Walker" wrote:
>
> I don't have a lot of detailed experience with redirects, so I'm
> kind of flying without a net (so to speak :-}):
>
> > From: Wes Peters <wes@softweyr.com>
> > Date: 1999-05-18 21:03:23 -0700
> > To: Jonathan Hanna <pangolin@home.com>
> > Subject: Re: Redirects and expire times
> > Jonathan Hanna wrote:
> > >
> > > What is the proper way of handling ICMP redirects? I expected
> > > host routes to be added with an expire time, but apparently
> > > they are permanent.
> > >
> > > I found one old reference to this, but no reply.
> > >
> > > > Date: Mon, 11 Mar 1996 15:09:15 -0600 (CST)
> > > > From: Scott Mace <smace@metal.neosoft.com>
> > > > To: hackers@freebsd.org
> > > > Subject: Redirects and expire times...
> > > > Message-ID: <199603112109.PAA15480@metal.ops.neosoft.com>
> > > >
> > > > I think it is a bug to add a host route after receiving a ICMP
> redirect
> > > > and NOT having any expire set on the route. If you have a
> default routed
> > > > host in a complex topology you can get into trouble when the
> topology changes.
> >
> > I agree. At Xylan, we had numerous customer complaints about redirects
> > filling the routing table and the only way to clear them (4.2 BSD based
> > stack) was to reboot the switch. We added a 10-minute timeout on all
> > redirect routes, figuring that redirects SHOULD be the exception rather
> > than the rule. YMMV. We've had no customer complaints since
> then. ;^)
> Seems to me that redirects would be used for a variety of reasons:
> (1) bad configuration; (2) multiple subnets on a single "wire" [so a
> router *might* want to use redirects to avoid duplicating traffic on
> the wire]; and mobility.
>
> If so, none of these seem to be especially "exceptions", but more
> like "rules".
Both (2) and (mobility) fall away as "rules" when you have VLANs and
Group Mobility - the ability to move to different physical ports and
have the VLAN follow you. ;^)
(Pardon the advertising, it is a valid point. Switched LANs are very
different creatures than the tradition hub/ethernet environment.)
--
"Where am I, and what am I doing in this handbasket?"
Wes Peters Softweyr LLC
http://www.softweyr.com/~softweyr wes@softweyr.com
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