Deploying fwknop
Now that you have a good understanding of the configuration options available in fwknop, it's time for a few meaty operational examples. In each case, the fwknop client is used to gain access to SSHD through a default-drop iptables policy after reconfiguration by the fwknop server. The network diagram in Figure 13-1 should help you to visualize these scenarios.
Figure 13-1. An SPA network
In each scenario below, the fwknop client is executed on the system labeled spaclient, and the SPA packet is sent to the system labeled spaserver. The dotted line in Figure 13-1 represents the SPA packet, and the follow-on SSH connection can only ...
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