Update README.md

README.md

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 Azure Automation solution for managing packet capture using Azure Network Watcher.
 
 [![Deploy to Azure](http://azuredeploy.net/deploybutton.png)](https://portal.azure.com/#create/Microsoft.Template/uri/https%3A%2F%2Fraw.githubusercontent.com%2FStratusOn%2FNetworkWatcherAutomation%2Fmaster%2FNetworkWatcherDeployment%2Fazuredeploy.json)
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+## Limitations:
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+* Lack of support for VMs across multiple resource groups or subscriptions. Only VMs in a single resource group can be specified.
+* Packet captures are limited to 5 hours. This is a Network Watcher limitation.
+* Only 10 packet capture sessions can be available at any time (also a Network Watcher limitation). Older sessions can be deleted which does not impact the corresponding packet capture logs.
+* No individual VM filters. The same packet capture filter should be applicable to all VMs specified.