When running your Exchange servers in a co-existence environment with an older version of Exchange you might notice some event 2002 warnings in your application log.
Log Name: Application
Source: MSExchange Front End HTTP Proxy
Date: 1-12-2017 11:25:03
Event ID: 2002
Task Category: Core
[Eas] The number of outstanding requests for guard TargetBackend(“<servername>”) has exceeded the max limit 150. Current request will be rejected.
The event is a warning and dispite the message description no connection are being blocked as a result of this. These event do generate a bit of clutter in your eventvwr which you can avoid by increasing these limits.
To do this you need to modify the web.config of the corresponding protocol. You have to edit the file on each Exchange server with the Client Access Server role.
- for ActiveSync and EAS: $installfolder\Exchange Server\V15\FrontEnd\HttpProxy\sync
- for OA, RPC/http: $installfolder\Exchange Server\V15\FrontEnd\HttpProxy\rpc
Before editing the web.config file be sure to make a backup of the file first.
In these files edit or create the entry in the existing <appsettings> configuration section. Substitute the <value> with the limit you want to use. The default value is 150.
<add key=”HttpProxy.ConcurrencyGuards.TargetBackendLimit” value=”<value>” />
After updating the web.config file you have to recycle the applicable IIS Application pool. Those are: MSExchangeSyncAppPool and/or MSExchangeRPCProxyAppPool depending on which web.config file you updated.
Monitor your application eventviewer log to see if you have increased the value enough.
I hope this was informative. For questions or comments you can always give a reaction in the comment section or contact me: