What is IPsec?

What is IPsec? What is IPsec? Wikipedia: Internet Protocol Security (IPsec) is a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a communication session.

What is IPsec anti-replay protection?

IPSec provides anti-replay protection against an attacker who duplicates encrypted packets with the assignment of a monotonically increasing sequence number to each encrypted packet.

How to test if an IPSEC tunnel is working?

The easiest test for an IPsec tunnel is a ping from one client station behind the firewall to another on the opposite side. If that works, the tunnel is up and working properly.

How does QoS affect IPSec packet delivery?

With the Cisco IOS implementation, IPSec encryption happens before QoS in the egress direction. Certain QoS features, such as Low Latency Queueing (LLQ), can cause IPSec packet delivery to become out-of-order and dropped by the receiving endpoint due to a replay check failure.