[ILUG] Bonding as Fallover?

[Gareth Eason]

Frank Murphy (Frankly3D) wrote:
> I've used bonding bond0(eth0,1) before on my file-server.
> 
> Am thinking of using it to create fallover between isp1 (dsl), and isp2
> (cable), on a new server. Am I on the right track, or is there something
> easier\better.
[snip]

	Hi,

	In short - no - bonding is not what you want to look at for this case.

	In long:

	Bonding requires that all interfaces begin and terminate in the same
layer 2 domain, typically - this means that they start on multiple
network cards in the same server, and terminate on multiple ports on the
same physical switch. Typically load sharing is done by using MAC
address or source IP address (which means that bonding only gives n *
link capacity throughput in the case where there is an even traffic
distribution across an even MAC/IP address distribution.)

	So, in summary, bonding is absolutely not the right answer for you, and
you might want instead to look at static routes with some kind of
failover script (take a look at linux-ha), using some intelligent
routers, or getting your own BGP AS number, which is the only way to
truly share and fail traffic over between multiple ISPs.

	As I contemplate hitting send, a second idea strikes me - if you use
IPv6 only, you can set up a tunnel routing your IPv6 prefix over your
primary ISP's v4 connection. If that fails, bring up the same tunnel
over your backup connection, et viola: your IPv6 has failed over. This
does rely on being able to detect failure, set up appropriate IPv4
routing for the tunnel, and of course configure an IPv6 prefix to route
over a tunnel (all relatively easy, for some values of easy.) It also
limits you to using tunnels (which kinda sucks) and only works for IPv6.

	Of course, you could do exactly the same for IPv4, but same limitations
apply and you'd have to find an IPv4 tunnel broker. IPv6 tunnel brokers
are readily available ( http://sixxs.net & Hurricane Electric, to name
but two.)

	Hope this helps.

	Best regards,
	-->Gar