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How to load balance two ESA

Hi Team,

I would like to know how to load balance ( create failover ) of one ESA to the other, and also how to check two ESAs are load balanced ?. Thank you  

Ken Stieers
VIP Advocate

Load balancing ESAs is all in how you get the traffic to them, they don't communicate or monitor one another.

The "easiest" is to put a load balancer cluster in front of them (F5, Citrix Netscaler, etc...), just like for web sites, but on port 25...

You can do some with DNS MX records.  you'll get something close to balancing... your DNS provider may allow you to "load balance", where they'll give out different addresses for the same request on a round robin or weighted fashion.

For outbound mail, your email software may be smart and balance which ESA it sends to, or it may not, in which case, a load balancer may be your best bet....

Look at the overview reporting page to see if they are getting similar traffic volumes....

Venkatesh Attuluri
Cisco Employee

to load balancing you use  DNS MX or A records by having equal weight  hosts

Sriram Subramanian
Cisco Employee


The load balance on the ESA needs to be done using the DNS MX or A record. Once DNS load balanced, it would be recommended to configure the ESA appliance in a cluster mode which would share the configuration between both the appliance.

Cluster configuration can only be configured using the command line.

You can find more information here:

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