Agents vs. "Connect All"
  • 17 May 2021
  • 2 Minutes to read
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Agents vs. "Connect All"

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Article Summary

This guide provides information on the difference between what agents and "Connect all" do and why we recommend using agents instead of using "Connect all"

What is "Connect All" (Auto Subnet agent)? 
The Auto Subnet agent is a function that allows SiteManager to connect to a whole subnet, or all agents available on SiteManager or both at once. For more information about configuring "Connect All" (Auto Subnet agent), please see: Link

What is an agent? 
An agent is something that you configure in a SiteManager in order for computers (LinkManager) to communicate with specific end devices on specific ports.

Why use an agent? 

Security 
The first reason is, of course, security. When using "Connect All", you will have access to the entire IP scope on the device side, resulting in access to all ports on every IP address. However, opening access to 16.7 million possible TCP connections might not be what you want. When using an agent you gain access to only the ports you need for the specific session. This could be 1 address with eg. 5 ports available. If you need access to more than one device at a time, you can group them together. (Read more about grouping agents together here: Link).

Functionality 
The second reason is what has most impact on your remote session. Agents are not just a security measure. They contain functionality and knowledge about the device that is connected. And they counter the lag and instability associated with the internet. If your latency drops below a specific threshold, the device at the other end will time out, and your upload may fail, or your login may be rejected. Siemens is a good example of how the agent counteracts low latency problems. The Siemens Ethernet agent will send a series of packets immediately after connecting to the panel without waiting for the payload from the LinkManager side. This ensures that a login to the Siemens panel is even possible, since it would fail on a "normal" VPN connection or with just "Connect All". Beckhoff is another example, who use "AMS net" for communication between the PLC and its gateway (not SiteManager). If the PLC is connected to a gateway and is using the AMS NAT protocol, SiteManager must be made aware of this. The option on the agent enables this and tells the SiteManager to connect to the PLC via a gateway.

To sum up, you can use the "Connect All" option if you have no other option (or just need a quick RDP session to a PC), but for normal use, you should use the agents.


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