nanog mailing list archives
Re: Should routers send redirects by default?
From: "Ricky Beam" <jfbeam () gmail com>
Date: Mon, 23 Aug 2010 17:39:47 -0400
On Sat, 21 Aug 2010 20:42:01 -0400, Mark Smith <nanog () 85d5b20a518b8f6864949bd940457dc124746ddc nosense org> wrote:
In IPv6, redirects serve two purposes, where as in IPv4 they only served one -
IPv4 redirects serve exactly the same two situations... both are situations where a router would be required to hairpin a packet -- either the destination is on-wire or the path to it is elsewhere on-wire.
Let's say host 1.100 has a default gw of 1.1 and no other routes. A packet destined for 2.1 would go to 1.1, even if 2.1 is on the same wire. Following old rules, 1.1 sends a redirect and drops the packet. Most hosts would ignore that redirect as it "makes no sense" (redirects are not a substitute for device routes. I've seen this happen too many times.)
Now, if 2.1 was behind 1.2, the redirect would tell 1.100 to go there instead.
(This isn't as much of a problem these days since routers don't to the "drop packet" part -- which used to be mandated by RFC. And "secondary" networks have given way to inter-VLAN routing.)
--Ricky
Current thread:
- Re: Should routers send redirects by default?, (continued)
- Re: Should routers send redirects by default? Owen DeLong (Aug 20)
- Re: Should routers send redirects by default? Christopher Morrow (Aug 20)
- Re: Should routers send redirects by default? Ricky Beam (Aug 20)
- Re: Should routers send redirects by default? Brandon Ross (Aug 20)
- Re: Should routers send redirects by default? Leen Besselink (Aug 20)
- Re: Should routers send redirects by default? Eric J. Katanich (Aug 20)
- Re: Should routers send redirects by default? Jack Bates (Aug 21)
- Re: Should routers send redirects by default? Jared Mauch (Aug 21)
- Re: Should routers send redirects by default? Mark Smith (Aug 21)
- Re: Should routers send redirects by default? Mark Smith (Aug 21)
- Re: Should routers send redirects by default? Ricky Beam (Aug 23)
- Re: Should routers send redirects by default? David W. Hankins (Aug 24)
- Re: Should routers send redirects by default? Mark Smith (Aug 24)
- Re: Should routers send redirects by default? Brandon Ross (Aug 20)
- Re: Should routers send redirects by default? Owen DeLong (Aug 20)
- Re: Should routers send redirects by default? Christopher Morrow (Aug 21)
- Re: Should routers send redirects by default? Ricky Beam (Aug 20)
- Re: Should routers send redirects by default? Brandon Ross (Aug 20)
- Re: Should routers send redirects by default? Butch Evans (Aug 24)
- Re: Should routers send redirects by default? Ricky Beam (Aug 20)
- Re: Should routers send redirects by default? Mark Smith (Aug 20)