Ifconfig eth1 down unsetting and setting the running flag on the other side.
 

Topology :

PC1 eth1 --------- eth1 PC2

PC1 and PC2 are linux pc's with linux 2.4 (or) 2.6 kernel installed on it.

Observations are done on both 2.4 kernel and 2.6 kernel

Problem explination:

1)PC1 "ifconfig eth1 down" on linux shell.
2)Check the "ifconfig eth1" on PC2
3) The running flags are unset first(disappear)and set(Re-appear) on the eth1 interface on PC2.
4) unset and set toggling happens with in short period of time about 1 or 2 secs.

This is clearly observed in linux 2.4 kernel with some time delay for the toggling, but 2.6 kernel this will happen every quickly...

What is the expected Behaviour:
================================

What all the flags should be present on PC2 machine eth1 interface, if a ifconfig eth1 down is issued on PC1 eth1 interface ?

Is this the right or normal behaviour.
If this is the general behaviour why this toggling of running flag happens.


Please can anybody help me by answering my question.


Thanks in advance.
bharath.

This is perhaps a symptom of ifplugd. My speculation is that taking one ethernet down causes the link-up status on the peer ethernet to go away, and the ifplugd daemon sees this, and de-configures the link. It is unclear why the link would then come back to life, however.
Is one or both of these a laptop? As I understand it, ifplugd is targeted primarily at laptops, which are prone to ad hoc connects and disconnects. Does the symptom persist if the connection between the hosts includes a network switch? If not, this would also point to ifplugd as a cause.

--- rod.

I would advise to monitor /var/log/messages while experimenting, on both PCs:
Probably what happens is one pc takes the Ethernet down, then the other thinks the cable has been unplugged. And with a switch in the middle, it would not happen. monitoring /var/log/messages would tell you exactly what happens.

Both PC1(76) and PC2(28) are Desktop PC's



[root@76 check]# ifconfig eth3
eth3 Link encap:Ethernet HWaddr 00:07:E9:A5:61:75
inet6 addr: fe80::207:e9ff:fea5:6175/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 <====running flag
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:936 (936.0 b)




[root@28 check]# ifconfig eth3
eth3 Link encap:Ethernet HWaddr 00:07:E9:A5:61:94
inet6 addr: fe80::207:e9ff:fea5:6194/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 <===== running flag
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:18 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:1404 (1.3 KiB)

ETH3 of PC1 and ETH3 PC2 and connected
======================================



[root@76 check]# ifconfig eth3 down <======== interface eth3 is made down.


[root@28 check]# ifconfig eth3
eth3 Link encap:Ethernet HWaddr 00:07:E9:A5:61:94
inet6 addr: fe80::207:e9ff:fea5:6194/64 Scope:Link
UP BROADCAST MULTICAST MTU:1500 Metric:1 <====== running flag disappered
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:18 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:1404 (1.3 KiB)

[root@28 check]# ifconfig eth3
eth3 Link encap:Ethernet HWaddr 00:07:E9:A5:61:94
inet6 addr: fe80::207:e9ff:fea5:6194/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 <=======running flag comes back
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:18 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:1404 (1.3 KiB)



[root@28 ~]# tail -f /var/log/messages
Jun 1 08:55:23 28 pam_limits[7917]: error parsing the configuration file
Jun 1 08:55:23 28 sshd(pam_unix)[7917]: session opened for user root by
root(uid=0)
Jun 1 08:55:23 28 PAM-env[7917]: Unable to open config file: No such fil
e or directory
Jun 1 08:56:45 28 PAM-env[7952]: Unable to open config file: No such fil
e or directory
Jun 1 08:56:45 28 pam_limits[7954]: can not read settings from /etc/secu
rity/limits.conf
Jun 1 08:56:45 28 pam_limits[7954]: error parsing the configuration file
Jun 1 08:56:45 28 sshd(pam_unix)[7954]: session opened for user root by
root(uid=0)
Jun 1 08:56:45 28 PAM-env[7954]: Unable to open config file: No such fil
e or directory
Jun 1 08:57:53 28 kernel: e1000: eth3: e1000_watchdog: NIC Link is Down <===down
Jun 1 08:57:55 28 kernel: e1000: eth3: e1000_watchdog: NIC Link is Up 10 <====up again
0 Mbps Full Duplex, Flow Control: RX/TX
Jun 1 09:01:01 28 pam_limits[7990]: can not read settings from /etc/security/limits.conf
Jun 1 09:01:01 28 pam_limits[7990]: error parsing the configuration file
Jun 1 09:01:01 28 crond(pam_unix)[7990]: session opened for user root by (uid=0)
Jun 1 09:01:01 28 crond(pam_unix)[7990]: session closed for user root
Jun 1 09:12:35 28 PAM-env[7913]: Unable to open config file: No such file or directory




[root@76 check]# tail -f /var/log/messages
Jun 1 08:01:01 76 crond(pam_unix)[4834]: session closed for user root
Jun 1 08:41:51 76 sshd(pam_unix)[4836]: authentication failure; logname= uid=0 euid=0 tty=ssh ruser=rhost=10.150.22.104

user=root
Jun 1 08:41:56 76 PAM-env[4836]: Unable to open config file: No such file or directory
Jun 1 08:41:56 76 pam_limits[4838]: can not read settings from /etc/security/limits.conf
Jun 1 08:41:56 76 pam_limits[4838]: error parsing the configuration file
Jun 1 08:41:56 76 sshd(pam_unix)[4838]: session opened for user root by root(uid=0)
Jun 1 08:41:56 76 PAM-env[4838]: Unable to open config file: No such file or directory
Jun 1 08:44:25 76 kernel: ADDRCONF(NETDEV_UP): eth3: link is not ready
Jun 1 08:44:25 76 kernel: e1000: eth3: e1000_watchdog: NIC Link is Up 100 Mbps Full Duplex, Flow Control: RX/TX
Jun 1 08:44:25 76 kernel: ADDRCONF(NETDEV_CHANGE): eth3: link becomes ready


This are the observation i made but couldn't understand much out of it, why is setting up the running flag back on the 28 host.

Any suggestions or help is highly appreciated.

Thanks,
bharath.