[3597] in linux-net channel archive
route cache weirdness
daemon@ATHENA.MIT.EDU (Jon Lewis)
Mon Jul 8 16:02:34 1996
Date: Mon, 8 Jul 1996 12:54:01 -0400 (EDT)
From: Jon Lewis <jlewis@inorganic5.fdt.net>
To: Linux Net Mailing List <linux-net@vger.rutgers.edu>
I'm a bit puzzled by the routing changes between 1.2.13 and 2.0.x. I
have 2 big terminal servers for which I've broken a /24 in half...routing
a /25 to each. On the mail server, I setup the following routes:
Destination Gateway Genmask Flags Metric Ref Use Iface
205.229.51.0 205.229.48.3 255.255.255.128 UG 0 0 295 eth0
205.229.51.128 205.229.48.4 255.255.255.128 UG 0 0 447 eth0
205.229.48.0 0.0.0.0 255.255.255.0 U 0 0 43 eth0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 3 lo
0.0.0.0 205.229.48.1 0.0.0.0 UG 1 0 3412 eth0
48.3 and 48.4 are the terminal servers (one runs 1.3.72, one 2.0.1).
Since I use these static routes, I was surprised to see lots of ICMP
redirects logged on the mail servers after the upgrade to 2.0.3.
Using a little perl script to scan the /proc/net/rt_cache, I found some
disturbing routes (trimmed down to the more interesting ones):
Iface Destination Gateway Use Metric Source
eth0 205.229.51.17 205.229.48.3 1 0 205.229.48.17
eth0 205.229.51.16 205.229.48.4 4 0 205.229.48.17
eth0 205.229.51.17 205.229.48.4 25 0 205.229.48.17
eth0 205.229.51.17 205.229.48.4 1 0 205.229.48.17
eth0 205.229.51.18 205.229.48.4 2 0 205.229.48.17
Since I have a static net route that should cover all these low
205.229.51. addresses, routing them to 205.229.48.3, why would
205.229.48.4 be issueing icmp redirects routing them to it, and why would
205.229.48.17 listen? Why would the cache have several wrong routes for
the same address?
Each terminal server has an appropriate static net route telling it that
the other half of 205.229.51 goes to the other term server.
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