pings return two at a time, every two seconds?

Issues related to configuring your network
gaylon
Posts: 21
Joined: 2005/03/23 16:35:33
Location: New Mexico, USA

pings return two at a time, every two seconds?

Post by gaylon » 2007/04/27 03:54:33

Normally ping replies come back one each second.
On this new CentOS 5.0 desktop machine, they come back two at a
time, every two seconds. So the output looks thus:

[me]# ping 192.168.169.17
PING 192.168.169.17 (192.168.169.17) 56(84) bytes of data.
64 bytes from 192.168.169.17: icmp_seq=1 ttl=128 time=457 ms
64 bytes from 192.168.169.17: icmp_seq=2 ttl=128 time=1490 ms
64 bytes from 192.168.169.17: icmp_seq=3 ttl=128 time=490 ms
64 bytes from 192.168.169.17: icmp_seq=4 ttl=128 time=1528 ms
64 bytes from 192.168.169.17: icmp_seq=5 ttl=128 time=528 ms
64 bytes from 192.168.169.17: icmp_seq=6 ttl=128 time=1557 ms
64 bytes from 192.168.169.17: icmp_seq=7 ttl=128 time=558 ms
64 bytes from 192.168.169.17: icmp_seq=8 ttl=128 time=1589 ms
64 bytes from 192.168.169.17: icmp_seq=9 ttl=128 time=590 ms
64 bytes from 192.168.169.17: icmp_seq=10 ttl=128 time=1624 ms
64 bytes from 192.168.169.17: icmp_seq=11 ttl=128 time=624 ms

or thus:

PING 192.168.169.17 (192.168.169.17) 56(84) bytes of data.
64 bytes from 192.168.169.17: icmp_seq=2 ttl=128 time=115 ms
64 bytes from 192.168.169.17: icmp_seq=3 ttl=128 time=1143 ms
64 bytes from 192.168.169.17: icmp_seq=4 ttl=128 time=143 ms
64 bytes from 192.168.169.17: icmp_seq=5 ttl=128 time=1177 ms
64 bytes from 192.168.169.17: icmp_seq=6 ttl=128 time=177 ms
64 bytes from 192.168.169.17: icmp_seq=7 ttl=128 time=1210 ms
64 bytes from 192.168.169.17: icmp_seq=8 ttl=128 time=210 ms

I see this effect when pinging any other machine (WinXP or CentOS-5)
from this one. Also when pinging this machine from any other.
But pinging between any two other machines gives the normal once
per second rhythm.
I swapped network cables between this machine and another
on the same desk. The effect stayed with the machine, rather
than moving with the switch-port and cable.
Booted to textmode (runlevel 3 instead of 5), and I get the
same effect.
Disabled SELinux & iptables. No improvement.

I opened the gnome-system-monitor, expecting to see the cpu
or network plots (set refresh interval to 0.25 seconds) have
a massive 0.5 Hz periodicity, but no such thing. Both are
mostly idle.

Web-browsing and everything seems to work, though it's slower
than my other machines. Hard to be sure, but it seems like
images which display as they're loading, grow in 'jumps' with
about two second periodicity.

Machine has Asus P5B-VM mobo w/ RealTek 8111B onboard Gigabit.
I also have a WinXP desktop, and a CentOS 5.0 server, using
the identical mobo. CentOS boxes are yum'd to latest, and
use latest ethernet driver from RealTek.

Anyone ever seen something like this?
Any suggestions for how to debug this?

Thanks!

gaylon
Posts: 21
Joined: 2005/03/23 16:35:33
Location: New Mexico, USA

Re: pings return two at a time, every two seconds?

Post by gaylon » 2007/04/27 04:01:49

I tried changing the ping interval to 1/4 second...
So now I get 8 replies in a burst, once every two seconds.

[root]# ping -c 30 -i 0.25 192.168.169.17

PING 192.168.169.17 (192.168.169.17) 56(84) bytes of data.
64 bytes from 192.168.169.17: icmp_seq=7 ttl=128 time=153 ms
64 bytes from 192.168.169.17: icmp_seq=8 ttl=128 time=1903 ms
64 bytes from 192.168.169.17: icmp_seq=9 ttl=128 time=1644 ms
64 bytes from 192.168.169.17: icmp_seq=10 ttl=128 time=1384 ms
64 bytes from 192.168.169.17: icmp_seq=11 ttl=128 time=1124 ms
64 bytes from 192.168.169.17: icmp_seq=12 ttl=128 time=874 ms
64 bytes from 192.168.169.17: icmp_seq=13 ttl=128 time=614 ms
64 bytes from 192.168.169.17: icmp_seq=14 ttl=128 time=354 ms
64 bytes from 192.168.169.17: icmp_seq=15 ttl=128 time=94.2 ms
64 bytes from 192.168.169.17: icmp_seq=16 ttl=128 time=1873 ms
64 bytes from 192.168.169.17: icmp_seq=17 ttl=128 time=1613 ms
64 bytes from 192.168.169.17: icmp_seq=18 ttl=128 time=1353 ms
64 bytes from 192.168.169.17: icmp_seq=19 ttl=128 time=1093 ms
64 bytes from 192.168.169.17: icmp_seq=20 ttl=128 time=843 ms
64 bytes from 192.168.169.17: icmp_seq=21 ttl=128 time=583 ms
64 bytes from 192.168.169.17: icmp_seq=22 ttl=128 time=323 ms
64 bytes from 192.168.169.17: icmp_seq=23 ttl=128 time=63.2 ms
64 bytes from 192.168.169.17: icmp_seq=24 ttl=128 time=1841 ms
64 bytes from 192.168.169.17: icmp_seq=25 ttl=128 time=1581 ms
64 bytes from 192.168.169.17: icmp_seq=26 ttl=128 time=1321 ms
64 bytes from 192.168.169.17: icmp_seq=27 ttl=128 time=1071 ms
64 bytes from 192.168.169.17: icmp_seq=28 ttl=128 time=811 ms
64 bytes from 192.168.169.17: icmp_seq=29 ttl=128 time=551 ms
64 bytes from 192.168.169.17: icmp_seq=30 ttl=128 time=291 ms

--- 192.168.169.17 ping statistics ---
30 packets transmitted, 24 received, 20% packet loss, time 7496ms
rtt min/avg/max/mdev = 63.268/973.338/1903.741/584.317 ms, pipe 8

The lost packets make sense, given the weird behaviour. This test must have ended 6/8 of the way through a period, so the last six packets hadn't come back yet.

gaylon
Posts: 21
Joined: 2005/03/23 16:35:33
Location: New Mexico, USA

Re: pings return two at a time, every two seconds?

Post by gaylon » 2007/04/27 04:06:16

So if the machine pings any other, I get the weird behaviour.
Also if any other machine pings this one.
But if this machine pings itself, the replies are one each second.
Dunno if that's a clue.

gerald_clark
Posts: 10642
Joined: 2005/08/05 15:19:54
Location: Northern Illinois, USA

Re: pings return two at a time, every two seconds?

Post by gerald_clark » 2007/04/27 13:21:43

Try a different port on your switch.

foxb
Posts: 1927
Joined: 2006/04/20 19:03:33
Location: Montreal/QC

Re: pings return two at a time, every two seconds?

Post by foxb » 2007/04/27 14:01:11

It sounds more like HW or LAN problem...

gaylon
Posts: 21
Joined: 2005/03/23 16:35:33
Location: New Mexico, USA

Re: pings return two at a time, every two seconds?

Post by gaylon » 2007/04/27 14:31:48

Swapped in a different switch. 100 Mbps, instead of Gigabit.
And tried a different cable from switch to this computer.
No improvement.

gaylon
Posts: 21
Joined: 2005/03/23 16:35:33
Location: New Mexico, USA

Re: pings return two at a time, every two seconds?

Post by gaylon » 2007/04/27 15:15:47

Found an old Netgear FA312 laying about.
Slotted it in, disabled the 8111b in bios, booted up.
CentOS quietly & automagically reconfigured for the new card (boy, *that* has gotten easier since way-back-when).
The two second problem is gone.

Remove the FA312, re-enable 8111b in bios.
The problem is back.

gaylon
Posts: 21
Joined: 2005/03/23 16:35:33
Location: New Mexico, USA

Re: pings return two at a time, every two seconds?

Post by gaylon » 2007/04/27 16:51:20

Moved the HDD into another machine (also P5B-VM w/ C2D E6300).
Problem gone.

Back into the first machine. Look around in bios.
Try SATA Configuration = Compatible (vs. Enhanced). No effect either way.
Try disabling JMicron PATA/SATA chip (JMB363). Problem's gone.
Try re-enabling JMicron. Problem's back.
Try JMicron Controller Mode = [BASIC] vs. [AHCI]. No effect either way.
Disable JMicron. Problem gone.
Of course, now I can't use the optical drive.
Perhaps I should order an SATA optical drive.

We have two other P5B-VM machines here ....
On my WinXP desktop, I use an external (USB) optical.
The server doesn't need an optical drive, so JMicron is disabled in the server's bios. I borrowed the usb external optical to install CentOS on the server.

I also tried enabling the JMicron ([BASIC] mode), but unplugging the optical drive's IDE cable from the mobo. The two-second-ping problem is gone! It seems the JMicron does not have to be disabled in bios, for the networking to behave. It just can't have a device plugged into it. Useful, that.

I pulled the Samsung SH-S182 DVDRW from my USB enclosure. Plugged it in, in place of the old LiteOn CDRW. Boot with JMicron in [BASIC] mode. The two-second-ping problem is back. (I'd figured *that* was a longshot.)

So I think, if my wife ever needs an optical drive, she's just gonna have to borrow my USB external.

Lenard
Posts: 2283
Joined: 2005/11/29 02:35:25
Location: Indiana

Re: pings return two at a time, every two seconds?

Post by Lenard » 2007/04/27 17:07:40

Hmmm................

Sounds like a possible BIOS issue (maybe a BIOS upgrade is available). What does the output from the typed command 'cat /proc/interrupts' minus the single quotemarks look like before and after disabling JMicron PATA/SATA chip (JMB363)???

gaylon
Posts: 21
Joined: 2005/03/23 16:35:33
Location: New Mexico, USA

Re: pings return two at a time, every two seconds?

Post by gaylon » 2007/04/27 18:41:26

JMicron DISABLED (no network problem):
[code]
[root]# cat /proc/interrupts
CPU0 CPU1
0: 138800 99860 IO-APIC-edge timer
1: 42 16 IO-APIC-edge i8042
8: 3 0 IO-APIC-edge rtc
9: 0 0 IO-APIC-level acpi
14: 34910 20164 IO-APIC-edge ide0
15: 0 0 IO-APIC-edge libata
50: 266 0 IO-APIC-level HDA Intel
169: 5268 5235 IO-APIC-level uhci_hcd:usb1, i915@pci:0000:00:02.0
177: 143 0 IO-APIC-level uhci_hcd:usb2, eth0
217: 740 0 IO-APIC-level uhci_hcd:usb3, ehci_hcd:usb7
225: 0 0 IO-APIC-level uhci_hcd:usb4, libata
233: 0 0 IO-APIC-level uhci_hcd:usb5, ehci_hcd:usb6
NMI: 0 0
LOC: 220278 231030
ERR: 0
MIS: 0
[root]#
[/code]

JMicron ENABLED (has two-second network problem):
[code]
[root]# cat /proc/interrupts
CPU0 CPU1
0: 340998 290057 IO-APIC-edge timer
1: 57 2 IO-APIC-edge i8042
8: 3 0 IO-APIC-edge rtc
9: 0 0 IO-APIC-level acpi
14: 33087 21706 IO-APIC-edge ide0
15: 0 0 IO-APIC-edge libata
50: 0 0 IO-APIC-level uhci_hcd:usb5, ehci_hcd:usb6
58: 266 0 IO-APIC-level HDA Intel
169: 20318 19196 IO-APIC-level uhci_hcd:usb1, libata, i915@pci:0000:00:02.0
177: 4999 0 IO-APIC-level ide2, uhci_hcd:usb2, eth0
225: 344 0 IO-APIC-level uhci_hcd:usb3, ehci_hcd:usb7
233: 0 0 IO-APIC-level uhci_hcd:usb4, libata
NMI: 0 0
LOC: 613965 622100
ERR: 0
MIS: 0
[root]#
[/code]

I'm very happy to provide whatever info to anyone with knowledge to figure out exactly what's going on here, so it can be fixed. There are zillions of these P5B-VM mobos out there, so it's well worth some of my time, to improve linux support for all of them. Though I can get by for now, without the working JMicron chip.

Motherboard BIOS is ver 0613 (2007/03/01), which is the latest at Asus.
Realtek driver is also latest: v 1.05 (2006/11/27)
I didn't do anything about a driver for the JMicron chip, since the CentOS 5 install disks did their thing without complaint.

Useless background info:
Now a few puzzle pieces start to come together, in the tapioca pudding I call a brain... When I first installed CentOS-5 on this box (I'd had WinXP working, to test the hardware), the ethernet wouldn't link. See my [url=http://www.centos.org/modules/newbb/viewtopic.php?topic_id=7838]earlier thread[/url] for the historical record.
In the course of debugging that, I flashed the bios to the latest (0613), which reset all bios settings to default, and required me to re-tweak the settings (disable the floppy, set audio output mode, etc etc etc). And the network mysteriously began working. But I didn't think to test how *well* it was working. I just assumed that 'yum update' took 14 hours to download 281MB (I have 1.5Mbps ISP) because CentOS-5 had just been released the day before and all the repos were overloaded. I now suspect that the problem was that the 8111B on this box was hobbled (perhaps only allowing a few pkts in a burst, every 2 seconds). I'd just not opened Firefox more than once or twice, and didn't notice that the network was super slow. I set this box aside and began installing CentOS-5 on the server. Eventually got to the setting up NFS exports, and came back to this box and booted it up as a client, to config & test. At some point I did a ping, and noticed the weirdness.

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