Counts ICMP Redirect messages received, which a router sends to tell a host a better next hop exists for a given destination. On a firewall, unsolicited or unexpected redirects are a known attack vector used to silently reroute traffic through an attacker-controlled path, so this counter climbing when the device isn't behind a router that legitimately issues redirects is worth treating as suspicious rather than routine. Example: icmpInRedirects incrementing on the external interface, where the gateway has no reason to receive redirects from the upstream ISP router, would warrant checking for a man-in-the-middle attempt.