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Subjectkiller

Yesterday, 2.1.111 killed a complete ethernet by booting diskless. (!)
While retrying rarp and bootp requests, the kernel responded to every
single arp request, claiming that the requested ip address belongs to
its NIC. (Note: This also happened with rarp turned _off_ in the
autoconfiguration section, so only bootp is used. So apparently there
is no relation btw the rarp code and this problem. The initial NIC+IP
configuration is the matter.)
What makes it even worse is that suns under Solaris 2.5.1 as well as
2.6 seemingly have a kernel bug wrt removing arp entries from the
cache (arp -d) and setting the arp cache timeout, which means that you
either have to down the interface and up it again or reboot the box
(ifconfig le0/hme0 down;ifconfig le0/hme0 up apparently fixes the
problems), once the "wrong news" has spread over the net. Either way,
it may be difficult to get rid of the problem without rebooting all
the machines at once (warning).

This is a mess, but one more: the kernel was not instructed via
cmdline root=/dev/nfs to boot on an nfs-rootfs. W/o cmdline the kernel
is supposed to use a root device which defaults to the one used at
compile time.
With 2.0, it was necessary to add this parameter to the cmdline for
the kernel to activate the network autoconfiguration procedures, "a
good idea".

Can somebody please reproduce that? Just compile a kernel with network
autoconfiguration turned on and a NIC driver for an attached NIC built
into the kernel, dump it to a diskette and boot it, without some
configuration elsewhere to catch the requests (let it time out and
watch what happens). You might not want to try this in a production
environment, even though it's funny. Prepare all other boxes to delete
the arp caches.
The relevant code hasn't been changed (significantly) during the last
versions of 2.1.x.

Discovered by poor Martin Walter, CC univ. o. Freiburg. :-)

Roman.
Computer Center University of Freiburg, Germany.
"The whole world is about three drinks behind." (Humphrey Bogart)






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