Bobby, Is this what you are looking for:
RHEL6: A Gratuitous Arp Is Not Sent for any IP Alias when the Linux System Boots http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&dlc=en&docname=c03391733 ________________________ Mike O'Reilly IBM Linux Change Team "Bauer, Bobby (NIH/CIT) [E]" <[email protected] To .gov> [email protected], Sent by: Linux on cc 390 Port <[email protected] Subject ist.edu> Some interesting bits about eth0:n 07/09/2013 07:10 AM Please respond to Linux on 390 Port <[email protected] ist.edu> This may be old news to some but it has cost us several hours so I thought I'd pass it on. We run multiple blog sites on single RHEL6 servers (multiple servers with similar configurations), each blog has an IP address defined with a ifcfg-eth0:n interface. Works fine except when we recently changed lpars and the mac address changed and the switches keep their ARP cache for 4 hours. The blogs defined with eth0:n were not available via http or even a ping. We had to do an arping to make them available. Of course it took a couple of tries at midnight to discover this. Turns out the eth0:n interfaces don't send a gratuitous ARP to tell folks 'here I am'. Haven't found that documented anywhere yet. The 'correct' method is to add IPADDRn and NETMASKn to ifcfg-eth0. That way a gratuitous ARP is sent both at IPL and ifup time. Of course now if you issue an 'ifconfig' command to check on your interfaces you only see the main IP address for eth0. You need to issue an 'ip addr' command to see secondary addresses. To take an IP address down or to delete it use 'ip addr del <ip>/<netmask> dev eth0 To add an IP address just add it to ifcfg-eth0 and do an 'ifup' Bobby Bauer Center for Information Technology National Institutes of Health Bethesda, MD 20892-5628 301-594-7474 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
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