User Freebsd said the following on 6/29/06 9:29 PM:
The other funny thing about the current em driver is that if you move an
IP to it from a different server, the appropriate ARP packets aren't
sent out to redirect the IP traffic .. recently, someone pointed me to
arping, which has solved my problem *external* to the driver ...
That's the second reason why I (still) avoid em in mass-aliased systems.
I have a single pool of IP addresses shared by many servers with
multiple aliases each. When someone leaves and frees an IP, it gets
reused and brought up on a different server. In case it was previously
handled by em, the traffic doesn't get redirected to the new server.
Similar thing happens even with machines with single static IPs. For
instance when retiring an old production system, I usually request a new
box to be brought up on a different IP, make a fresh install on
everything and test, swap IP addresses and reboot. In case of em, after
a soft reboot both systems are inaccessible.
A workaround is to power both of the systems down and then power them
up. This however cannot be done remotely and in case there were IP
aliases, they still don't get any traffic.
I have a third machine that uses an em driver, but its an older 4.x
kernel, and it operates perfectly ... no timeouts/hangs and sends out
the appropriate ARP packet ... all three servers are connected to the
same Cisco switch, with all ports configured identically, so it isn't a
switch issue, as someone else intimated ...
This seems strange, could depend on the chip version, who knows.
I still have many 4.x based machines, and both em issues (the card reset
on each alias and the arp packets not been sent when going down) were
present when I was doing my tests.
I check for these once in a while (a year or so), usually with the
latest major release branch.
We had a compatibility issue about a year ago with a (rather exotic?)
fiber NIC - 82545GM, where FreeBSD-4.x did better. The em driver coming
with 5.x didn't support that (or wasn't working as expected, I don't
remember the specifics), while the one coming with 4.x did, so we ended
up installing 4.11 then.
Regards,
Atanas
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