Counts ICMP Time Exceeded messages sent by the device, generated when it forwards a packet whose TTL just hit zero. This counter only increments when the gateway is acting as a transit router for traceroute-style traffic passing through it, so a rise here indicates increased diagnostic traffic transiting the box rather than anything targeting the gateway itself. Example: icmpOutTimeExcds ticking up steadily during a network mapping exercise by the ops team confirms the gateway is correctly responding to the traceroutes they're running through it.