I am not sure if we can not send attachments to the mailing list. There were
quite a lot replies before, but I got nothing back since attachements was
added. I will remove the attachments and send it again. Please have a look at
the email below. Thanks for your help.
---
Dear All,
Thanks for all your help. I will put all the comments together. Please have a
look if there is any clue on such ghost problem. I have also attached the log
files: dmesg, secure, messages. Please note that there is a message in secure
when it exited just now.
Oct 9 10:55:55 maya2012 su: pam_unix(su:session): session closed for user root
> Can you trigger the error reliably by doing something network intensive, like
> scp or rsync a large file? I've seen similar behaviour with a bad NIC that
> was in the process of dying.
Yes, I copied tens of Gb files using rsync. It worked well.
> That's very often a result of IP conflict. I'm assuming that you're
> connecting to an IPv4 address. If so, log in to your CentOS server and use
> arping to look for conflicts:
>
> # arping -c 2 D -I em1 <your address>
The IP is fixed to my server. The network administrator has checked the
address, and only this computer uses it. When I run the above command line, the
output is:
[root@maya2012 hwang]# arping -c 2 -D -I em1 222.200.125.5
ARPING 222.200.125.5 from 0.0.0.0 em1
Sent 2 probes (2 broadcast(s))
Received 0 response(s)
>> 1. Login via Mac, Windows, Linux systems from different computers.
>> 2. Modify sshd_config on the server as suggested by many posts:
>> TCPKeepAlive yes
>> ClientAliveInterval 60
>
> TCPKeepAlive is "yes" by default. ClientAliveInterval doesn't appear to be a
> valid setting. Either TCPKeepAlive or ServerAliveInterval could be useful if
> the problem were a stateful firewall which was dropping your connection from
> its state table, and then resetting the connection in response to a later
> packet from your client.
>
> Since those don't help, that tends to suggest that the problem isn't an
> intermediate host, but the server itself. Possibly an IP conflict. Also,
> check the output of "dmesg" to see if there are any problems recorded with
> the NIC. Check the output of "ifconfig" to see if there are TX or RX errors
> that increase when your connections are reset.
[root@maya2012 hwang]# ifconfig
em1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 222.200.125.5 netmask 255.255.255.128 broadcast 222.200.125.127
inet6 fe80::d6ae:52ff:fe6a:405e prefixlen 64 scopeid 0x20<link>
ether d4:ae:52:6a:40:5e txqueuelen 1000 (Ethernet)
RX packets 2865 bytes 396191 (386.9 KiB)
RX errors 0 dropped 180 overruns 0 frame 0
TX packets 510 bytes 55844 (54.5 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
em2: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
ether d4:ae:52:6a:40:5f txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 0 (Local Loopback)
RX packets 7 bytes 748 (748.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 7 bytes 748 (748.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
[root@maya2012 hwang]# ip -s -d l l
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode
DEFAULT
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 promiscuity 0
RX: bytes packets errors dropped overrun mcast
748 7 0 0 0 0
TX: bytes packets errors dropped carrier collsns
748 7 0 0 0 0
2: em1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode
DEFAULT qlen 1000
link/ether d4:ae:52:6a:40:5e brd ff:ff:ff:ff:ff:ff promiscuity 0
RX: bytes packets errors dropped overrun mcast
312908 2272 0 138 0 1081
TX: bytes packets errors dropped carrier collsns
43946 403 0 0 0 0
3: em2: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode
DEFAULT qlen 1000
link/ether d4:ae:52:6a:40:5f brd ff:ff:ff:ff:ff:ff promiscuity 0
RX: bytes packets errors dropped overrun mcast
0 0 0 0 0 0
TX: bytes packets errors dropped carrier collsns
0 0 0 0 0 0
Thanks,
Hua
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