Date: Tue, 26 Dec 1995 20:19:10 +0100 (MET) From: volf@oasis.IAEhv.nl (Frank Volf) To: freebsd-hackers@freebsd.org, bind-users@vix.com Subject: Freebsd IP alias and BIND Message-ID: <199512261919.UAA05384@oasis.IAEhv.nl>
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Hi and merry Xmas to you all,
This message is sent to both freebsd-hackers and bind-users because I
haven't figured out yet whether to blame FreeBSD, bind ore myself. I know this
(or similar) problem have been the topic of bind-users before, but as far
as I know there has not been a fix for it.
THE SETUP:
FreeBSD 2.05 box (pentium 90) and bind-4.9.3beta32. The FreeBSD box has
a IP address (192.87.208.2) and an IP alias (194.151.64.2).
The alias is used because we are in process of moving to a new IP netblock
and we want both the old and the new nameserver addresses to be valid in
the transition period.
THE PROBLEM:
When a query is sent to the IP alias two responses are generated: one
response with the real IP address as the source address, the other one with
the alias address as the source address:
17:02:20.146789 192.87.209.4.53 > 194.151.64.2.53: 52731+ NS? tue.nl. (24)
17:02:20.148820 192.87.208.2.53 > 192.87.209.4.53: 52731* 3/0/3 NS kweetal.tue.nl. (144)
17:02:20.150752 194.151.64.2.53 > 192.87.209.4.53: 52731* 3/0/3 NS ns1.surfnet.nl. (144)
On a UNIX system runing BIND, the bogus response triggers the "response from
unexpected source" message, but has no other effects. Some dialin software
however (older versions of trumpet winsocket if I recall correctly) do not
handle this correctly and cause the nameserver request to timeout if the
wrong response is received first.
THE CAUSE:
I'm not sure. Since you can see in the tcpdump that the responses are
different (round robin is turned on), it seems that bind gets or processes
the incoming UDP package twice. I however don't know, if this is caused
by bind or by the FreeBSD kernel.
THE SOLUTION:
Please tell me :-)
Regards,
Frank
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Frank Volf - Internet Access Eindhoven - Digitale Stad Eindhoven
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