Re: Equal Cost Multipath?

Matthew G. Marsh (
Wed, 1 Sep 1999 19:41:06 -0500 (CDT)

On Wed, 1 Sep 1999, Brian Anderson wrote:

> On Tue, 31 Aug 1999, Matthew G. Marsh wrote:
> > Sorry to butt in but there is an alternative. Get Alexey's IP utility and
> > set up a single default route with multiple endpoints. Then each PACKET
> > goes via each path. O' course you can confuse apps under Windorks that
> > don't understand this method (as in you are talking directly to a NT Quake
> > server... 8-})
> Hrm... I'd rather see less efficient balancing, with less error, than
> better balancing but with less problems...

Actually the real problem is that the server tries to treat the incoming
as two different connections (as it does have two different IP addresses).
This is OK for web stuff. Now one of the wierder alternatives to this is
to use policy routing so that the packets will still balance one by one
however you can specify the 'src' parameter to the default routes and get
a single outgoing address balanced across the cable modems. However this
would force all replies to come in on that specified address. What I think
you could do but have not tried myself is use fwmark to do this on a per
protocol data stream. IE: All quake with one IP all http with the other.
... Hmm you know I may just have to play with that.... 8-}

> > ip route add default nexthop eth0 nexthop eth1
> that's interesting tho... i grabbed the utility, and will probably try
> both ways and see which works better.
> > Hehehe - Actually the above default route will split the packets and give
> > new addresses as well due to the ip masq occuring AFTER the routing code
> > call. Just need single masq call in ipchains as if a standard single out
> > box.
> >
> > ipchains -A forward -j MASQ -s meownnet/cidr -d 0/0
> now this should be the same if i add 2 default routes, right?

Yes. Unless you start playing with policy routing but then your default
route structure also changes.

> while i'm at it, does anyone have any suggestions for an app to monitor
> traffic and see if this is really working?
> brian

Let me know what you end up seeing. Thanks!

Matthew G. Marsh, President
Paktronix Systems LLC
1506 North 59th Street
Omaha NE 68104
Phone: (402) 932-7250

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