multiple links

Unanswered Question
Aug 15th, 2007

dear all,

i have two internet links (dsl), having 1 cisco 1811 router, both of these are on (dedicated 8 port ) switch and a link to router (fa0). fa1 to lan . i want to setup load balancing (80%-link1 , 40% of link 2), and in case of failure of link-1 all traffic redirect to link-2.

is it possible without bgp :) (because i dont want any configuration on ISP end)


I have this problem too.
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Paolo Bevilacqua Wed, 08/15/2007 - 10:24

Do you have two outside NAT interfaces now ?

If so you should also have two default routes. To balance traffic, manually add some route to popular destinations via an ISP or the other.

For backup, you need to use track, it is a bit complicated, first let us know how do you connect with the adsl, staticp IP, PPPoE or what else.

ammadshah Wed, 08/15/2007 - 10:40



| |----ether---[adsl-2]---wan



as you can see in diagram, adsl-1 is isp1 , and adsl-2 is isp2, and have static (public) ip addresses on both links,

fa0 and fa1 have also static public ip address on cisco-router.

adsl-1 1Mb (data dedicated)

adsl-2 512Kbps (voice dedicated)

since there isn't any utilization of adsl-2,

so i want to utilize it 40-75% also for data, and in case of adsl-1 goes down(since its ethernet, and if isp link is down ehternet adsl-1 link will be up but no data), all traffic redirect to adsl-2.

is this possible

Paolo Bevilacqua Wed, 08/15/2007 - 11:05

It is possible if you use NAT for both links.

Make a NAT configuration for adsl-2 as well.

Point some routes to some destination using that interface.

After you have this part working when can suggest a tracking configuration so the static default route via adsl1 is subject to actual reachability of some object on the internet.

ammadshah Wed, 08/15/2007 - 11:13

you are right, but there is also a cache(proxy) server that is working as transparent proxy and firewall for lan.

(linux 2.6)

Paolo Bevilacqua Wed, 08/15/2007 - 11:45

If it is on the internal LAN (nat inside0doesn't matter, it is treated like any other, PC, the router decides where to send traffic.


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