Is load balancing outbound Internet traffic old school?

[rpastor]

Hello,

This is a follow-up to an earlier post related to the question of load balancing outbound traffic over a multihomed internet connection.  Our company is a school that has its own address space, external DNS, and two ISPs. If most of our internet traffic consists of downloads to students inside our network, is it customary in this situation to allow all outbound traffic to exit one link while keeping that link as well as the second link active for  incoming (downloaded) traffic?  In other words, if both  links are the same speed, and the amount of outbound (upstream) traffic  is minimal, is it reasonable to allow that outbound traffic to head out  just one of the links, but allow incoming traffic to enter both links (which it will do on its own)?   (auto-failover would still be configured, which is a different issue). 

A few years ago, I studied BGP and the ideas of setting a higher local preference for certain outbound traffic, etc, and redistributing to an IGP.  But these ideas seem outdated now in the days of video streaming.  The answer seems obvious, but I'd like to hear it from an expert, if possible.

Thank you very much,

Richard Pastor

[paolo bevilacqua]

Do you have BGP? Even if not, NAT based load balancing works well enougha and gives few options for the details. You can search the forum or cisco.com about.

[Joseph W. Doherty · Accepted solution]

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Posting

If outbound usage is as light as you note, I too probably wouldn't worry about outbound load balancing.  If I did worry about it, I would probably use OER/PfR (if supported) to automate it.  I would, however, insure there was outbound QoS (e.g. fair queuing) with shaping (if needed) to insure one to few high rate flows weren't especially adverse to other flows.

Inbound, traffic will routinely take what it considers the "best path" from its source to your site.  If you use ISP specific NAT, inbound load balancing will sort of track your outbound balancing.  However, as you noted using your own public IP address space, inbound Internet load balancing would take some work to accomplish.

[rpastor]

Thank you