Date: Tue, 22 Nov 2011 22:58:14 +0100 From: Kees Jan Koster <kjkoster@gmail.com> To: Gary Gatten <Ggatten@waddell.com> Cc: "'freebsd-questions@freebsd.org'" <freebsd-questions@freebsd.org> Subject: Re: Diagnosing packet loss Message-ID: <4B28ADC5-8325-442E-8F02-9AE3535D8C6D@gmail.com> In-Reply-To: <2973_1321996526_4ECC10EE_2973_123_1_D9B37353831173459FDAA836D3B43499D2C69D77@WADPMBXV0.waddell.com> References: <2973_1321996526_4ECC10EE_2973_123_1_D9B37353831173459FDAA836D3B43499D2C69D77@WADPMBXV0.waddell.com>
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Dear Gary, Thank you for your reply. Your comment about dupe IP triggered something = that I failed to mention: the interface is aliased. It has two IP = addresses. IP address a and it has an alias IP address b. I just tested = binding mtr to each of these interfaces separately to measure packet = loss. If I use mtr to measure packet loss from saffron (the stricken machine) = to cumin (another machine in a different data center) I see the = following: saffron (ip address a) -> cumin: packet loss saffron (ip address b) -> cumin: no packet loss cumin -> saffron (ip address a): packet loss cumin -> saffron (ip address b): no packet loss This is consistent from running mtr for 5 minutes straight. This to me = shows that the hardware is fine. Using the alias IP address I can run = with no packet loss for as long as I like. Hum.... Could it be that my switch does not support IP aliasing? Then = why is there packet loss only on one IP and not on both? This is getting weirder and weirder. Kees Jan On 22 Nov 2011, at 22:15, Gary Gatten wrote: > Well, 1% is not good but I've seen worse for sure! Sounds like you = tried the obvious. I would recommend a different IP to rule out a dupe = ip; else it must be NIC related - either hardware or driver. Also, = perhaps swap cables and ports with a working machine and see if the = problem follows or stays put. >=20 > ----- Original Message ----- > From: Kees Jan Koster [mailto:kjkoster@gmail.com] > Sent: Tuesday, November 22, 2011 02:33 PM > To: freebsd-questions@freebsd.org <freebsd-questions@freebsd.org> > Subject: Diagnosing packet loss >=20 > Dear All, >=20 > I am stuck with a machine that shows serious packet loss (about 1% of = all traffic is dropped). I tried the obvious (new network cable, = different switch port, different ethernet interface on the machine), but = the problems remain. >=20 > Another machine that sits in the same rack and is hooked up to the = same switch shows no such packet loss issues. The problematic machine is = a dual Opteron with FreeBSD 8.2-STABLE from Thu Aug 11 14:05:47 CEST = 2011. >=20 > The machine is lightly loaded. A MySQL slave is running, but the = machine is not serving queries. Plus a Munin server process. >=20 > I am at a loss where to start diagnosing this. Can you advise me where = to look? Are there network buffers that may be overflowing? > -- > Kees Jan >=20 > http://java-monitor.com/ > kjkoster@kjkoster.org > +31651838192 >=20 > Change is good. Granted, it is good in retrospect, but change is good. >=20 > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to = "freebsd-questions-unsubscribe@freebsd.org" >=20 >=20 >=20 >=20 >=20 > <font size=3D"1"> > <div style=3D'border:none;border-bottom:double windowtext = 2.25pt;padding:0in 0in 1.0pt 0in'> > </div> > "This email is intended to be reviewed by only the intended recipient > and may contain information that is privileged and/or confidential. > If you are not the intended recipient, you are hereby notified that > any review, use, dissemination, disclosure or copying of this email > and its attachments, if any, is strictly prohibited. If you have > received this email in error, please immediately notify the sender by > return email and delete this email from your system." > </font> >=20 -- Kees Jan http://java-monitor.com/ kjkoster@kjkoster.org +31651838192 I hate unit tests; I much prefer the illusion that there are no errors = in my code. -- = Hendrik Muller
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