On Thu, Aug 10, 2006 at 11:45:03AM -0300, Fabio Meneses wrote:
> Anyone know any alternative to Cisco's GLBP ?
> Its more like an redundancy solution, but provided with Load Balancing
> capabilities, for L3 devices.

OpenBSD's CARP protocol (also available on FreeBSD and Linux, among
others) has the same functionality. In fact, CARP's arpbalance feature
seems to predate GLBP, although I've never seen OpenBSD credited for the

Note that the ARP-based load balancing found in both CARP and GLBP share
the same limitations:

- ARP balancing only works on the local network segment. It cannot
balance traffic that crosses a router, because the router itself will
always be balanced to the same virtual host.

- Secondly, ARP load balancing can lead to asymmetric routing of
incoming and outgoing traffic. If you're using a packet filter that
does state tracking, this may cause problems as state values will be
out-of-sync. Proxies or NAT can be used to avoid this asymetric route

More information can be found in the OpenBSD carp(4) manual page:

Disclosure: I'm one of the primary authors and maintaners of CARP.


Ryan T. McBride, CISSP - mcbride@countersiege.com
Countersiege Systems Corporation - http://www.countersiege.com
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