Yesterday we planned to have a backup of our Proxy Server (Squid) while to reconfigure the original one because we face space shortage while SARG (Squid Analysis Report Generator) updates to be saved on the drive. we done with backup proxy server on RHEL-4, everything done normally the configurations, copy the files like dhcpd.conf, squid.conf, iptables to the backup and bring on a network and then we turn off the master server and check the internet connectivity and security so everything goes smoothly. After a while complaints comes from different departments that our system got stucked and then start and then stucked............! but the shocking moment was our Operations department complaint that BILLING SERVER (AIX-Server) also get stucked and all users were bussy in data entry.....ooooooooops ?
After that i checked our Head Office router using ping and it shows the link up, down, up down, then i checked our router so same problem..................!
After searching and finding we came to know that by mistake at time when we bring the backup proxy on a network we plug-in another connection to switch with the backup port of the radio room and then backup proxy link was already connected to switch, so two connection of the router and that cable are drop into hub in radio room so loops were created and stuck our network.