What event has occurred if a router sends a notice level message to a syslog server?

Syslog messages are categorized by severity levels, ranging from 0 (Emergency) to 7 (Debugging). The "notice" level, which has a severity value of 5, is defined for "normal but significant conditions." An interface changing its line protocol status (e.g., going from down to up, or up to down) is a classic example of such an event. While it is a normal part of network operation, it is significant enough to warrant a notification to the network administrator. The common LINEPROTO-5-UPDOWN message is a notice-level message that indicates this exact event has occurred.

A. A TCP connection being torn down is a routine operational event and is typically logged at the "informational" level (level 6), which is less severe than "notice."

B. ICMP is a connectionless protocol. The concept of building or tearing down an "ICMP connection" is technically incorrect, making this option invalid.

D. An expired certificate is a potential security or operational failure. This event would be logged at a higher severity level, such as "warning" (level 4) or "error" (level 3).

1. Odom

W. (2020). CCNA 200-301 Official Cert Guide

Volume 2. Cisco Press.

Chapter 24

"IP Services

" Section "Syslog

" Table 24-2 "Syslog Severity Levels and Keywords." This table defines severity level 5 (notice) as "Normal but significant conditions." The accompanying text explicitly uses an interface going up or down as an example of a notice-level event.

2. Cisco. (2023). Cisco IOS XE Amsterdam 17.3.x (Catalyst 9300 Switches) System Message Guide.

Chapter: "System Message Logging

" Section: "Severity Levels." This official documentation defines level 5 (notifications) as "Normal but significant conditions." It also documents the LINEPROTO-5-UPDOWN message

which is a level 5 message stating

"Interface [chars]

changed state to [chars]." This directly confirms that an interface status change is a notice-level event.