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Using Nmap to Fix a Problem

Mar 05, 2010, 22:02 (0 Talkback[s])

[ Thanks to Jay Fink for this link. ]

"Fixing a Problem with Nmap

"Ever had an ipv4 network address that is supposed to migrate over via a high availability mechanism simply not work or even stranger if there were several addresses some do and some do not? An experienced network administrator probably has seen mysterious non-migrating addresses, however, within this context is presented a rather interesting solution to when it has been observed.

"The Setup

"For simplicity two addresses will be used, the idea being if a service or server in part of a 2 node high availability cluster are detected down via a heartbeat check the node that is up takes over (unless it is the one already holding the addresses). There are some details that need to be presented as well:

"The compute nodes are on the same logical but different physical networks and communicate via a switch.

"There is a cisco global site selector in front of the compute nodes.

"The compute nodes are running a recent version of Red Hat Linux."

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