On 9/11/07, Jun Salen nokijun@yahoo.com wrote:
Hi List,
My Mail/Proxy server has from time to time refuse
to
accept accept network connection. If I restart the network service, the service will again start to accept connection but after some time will again refuse connection. I use CentOS 4.5 with Squid, DansGuardian, Postfix. Please can someone point me what are the possible cause of this. Thank you.
In addition to my posting above. When I make ping to other machine from the server, the server will again restore and accept connection. This is weird, so my temporary solution is to let the server continually ping other machine. Please help. Thanks again.
Ping is a very cheap and acceptable solution !
Anyway you'r certainly curious about the problem :-) This is a problem about ARP request. Maybe another machine with low activity share the same IP or your swith/hub is badly configured ! You can use arping to detect any device with the same IP and tcpdump to look for arp request."arp -an" will show you the arp table.
Regards
junji aisalen.wordpress.com Linux Registered User #253162
Send instant messages to your online friends
CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
On 9/12/07, Jun Salen nokijun@yahoo.com wrote:
On 9/11/07, Jun Salen nokijun@yahoo.com wrote:
Hi List,
My Mail/Proxy server has from time to time refuse
to
accept accept network connection. If I restart the network service, the service will again start to accept connection but after some time will again refuse connection. I use CentOS 4.5 with Squid, DansGuardian, Postfix. Please can someone point me what are the possible cause of this. Thank you.
In addition to my posting above. When I make ping to other machine from the server, the server will again restore and accept connection. This is weird, so my temporary solution is to let the server continually ping other machine. Please help. Thanks again.
Ping is a very cheap and acceptable solution !
Anyway you'r certainly curious about the problem :-) This is a problem about ARP request. Maybe another machine with low activity share the same IP or your swith/hub is badly configured ! You can use arping to detect any device with the same IP and tcpdump to look for arp request."arp -an" will show you the arp table.
Regards
junji aisalen.wordpress.com Linux Registered User #253162
Send instant messages to your online friends
CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
-- Alain Spineux aspineux gmail com
When I do /sbin/arp -an in the server box it does not contain entries for ip address where the server, it is ok?
I have the same here, I'm not surprised.
I observed that when I ping the server from other machine, it replies but from time to time displays time-out. We use this server for our mail and proxy so it is affecting us when time outs occur. Tsk tsk.
Every time the server ping (or open an IP connection) one of your client, it "announce" its MAC address on the network. Switches and bridges will learn this information for some minutes and later redirect client responses or new connections directly to your server. When the MAC cache is expired, switches have to learn by them self, and depending the network topology, the configuration of the switch, or some bug in the switch itself this could fail.
Try to replace your switch.
junji aisalen.wordpress.com Linux Registered User #253162
Send instant messages to your online friends http://uk.messenger.yahoo.com _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
-
Alain Spineux -
Jun Salen