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I noticed in my routes output in RHEL6 (and most 2.6.x series Linux), for every interface I see the creation of the following route in my kernel routing table:

169.254.0.0     0.0.0.0         255.255.0.0     U     1018   0        0 bond0
169.254.0.0     0.0.0.0         255.255.0.0     U     1019   0        0 bond1
169.254.0.0     0.0.0.0         255.255.0.0     U     1020   0        0 bond2

My understanding is that the link-local addresses are used when auto address configuration fails (when dhcp breaks). When dhcp fails the system will assign itself an available link-local address (more or less).

In your guy's experience, are these necessary? I'm utilizing manual/static IP assignment in my network, so there is no auto-address configuration. Therefore, there is no chance that auto-address configuration would fail. Can I safely remove these routes?

Or is there some other hack/reason I should keep these guys?

Diego

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1 Answer 1

up vote 1 down vote accepted

Link Local address space (RFC 3927) is a nice idea for client addressing, but in practice is rarely used for anything except catching an administrator's eye when reading ipconfig/ifconfig output to learn why someone's PC isn't on the network.

In fact, on my servers, I don't want link local addressing. I don't want servers to have a chance at being assigned a different address space. I don't even like link local address space on client PCs, but that's another post.

There is no kernel level wonkery going on with link local addressing that I am aware of. In fact, link local tables should simply be predefined in /etc/sysconfig/static-routes. Yank 'em, I say.

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Thanks David, thats exactly what I needed to hear. I'll go ahead and remove these guys. In terms of the kernel level wonkery, here is an excerpt from the route command manpage: "Route manipulates the kernel's IP routing tables." I'm not sure about other distro's, but on RHEL5 & 6, /etc/sysconfig/static-routes does not exist. These link-local routes are created per "physical" interface on the system. I say physical, because these don't show up for vlan'd tagged interfaces, but they do on ethernet and bonds. –  slugman Apr 27 '12 at 8:03

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