Is it possible to have two ISP connection internet load balancing?
We are having two different ISP's internet connection (20 Mbps & 8 Mbps) for the internet but we are using only one for internet and for site-to-site VPN.
But what we need is to use one for internet & VPN and the other one as internet load balancing.
you can do load-sharing per src-dst with IP CEF using static routing so yes it is possible and you'll find examples hers in the docs.
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There may be several alternatives to consider. As Alain has suggested one alternative would be to configure two static default routes, one to each ISP. The two static routes would result in some traffic going to one ISP while other traffic goes to the other ISP.
Another alternative to consider would be to configure a static default route to the ISP with higher bandwidth and then to use Policy Based Routing to send some types of traffic out the link to the other ISP. This would give you load sharing based on type of traffic.
And another alternative to consider would be to run BGP. Many people find that Internet connection through two separate ISP is the threshold where it is beneficial to run BGP.
I would also comment that in terms of load sharing it is easier to load share looking at the traffic that is sent out from your network and more difficult to load share looking at the traffic that is sent from the Internet into your network.