By Lawrence Abrams
Publication Date: 2026-01-08 20:40:00
Multiple Cisco switch models are suddenly experiencing reboot loops after logging fatal DNS client errors, according to reports seen by BleepingComputer.
Starting at approximately 2 AM, what appears to be a firmware bug in the switches’ internal DNS client service began treating DNS lookup failures as fatal errors, causing affected devices to reboot repeatedly.
Switches impacted by the bug are logging fatal errors similar to the following before rebooting:
DNS_CLIENT - SRCADDRFAIL - Result is 2. Failed to identify address for specified name 'www.cisco.com.', requested addr type 2. ***** FATAL ERROR ***** Reporting Task: DNSC. [debug data] ***** END OF FATAL ERROR *****
Based on reports from administrators who contacted BleepingComputer, Reddit discussions, and Cisco Community forum [1, 2] posts, the fatal errors originate from the DNSC (DNS Client) task and occur when the switches attempt to resolve “www.cisco.com” and NTP time…
