Tom Matthews writes: > Thankyou Alex for the thorough correction on the specifics of IPMP failure > detection, I had completely forgotten about the better practice of using > host-routes. > I was merely suggesting one use for multiple default routes in response to > the question posed "So what's the purpose (or semantics) of 'multiple default > routers?' "
For that original question (not related to IPMP), the system will use all of the configured default routes in an unspecified way. Currently, when we attempt to contact a remote (off-link) IP address that we either have never contacted before or that we haven't talked to in a "while," we'll use a round-robin policy to select the next default route to use. If we've talked to a remote address recently, then we'll use the same default route again, until the route is deleted, TCP reports retransmissions, or we go idle for a "while." By specifying multiple default routes, you're saying that there are multiple equivalent ways to leave your local subnet and that each of these next-hop routers is exactly equivalent for reaching all remote destinations. If any of that is not true, then don't configure your routes like that. (Be especially careful not to specify something as a "default router" if it cannot forward to all remote IP destinations -- you'll end up with unreliable connections, black holes, and excessive ICMP redirect traffic.) More generally, future releases of OpenSolaris may use other criteria for choosing among multiple routes of any kind (not just default routes). One obvious (but not currently implemented) way to do this is with a flow-identifying hash. This is a nice stateless mechanism that works well with ECMP (Equal-Cost Multi-Path) routing and minimizes reordering. -- James Carlson, Solaris Networking <[EMAIL PROTECTED]> Sun Microsystems / 35 Network Drive 71.232W Vox +1 781 442 2084 MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677 _______________________________________________ networking-discuss mailing list [email protected]
