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Cisco Switches Affected by DNS Client Bug Causing Reboot Loops

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Last updated
1 unique sources, 1 articles

Summary

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Multiple Cisco switch models are experiencing reboot loops due to a DNS client bug. The issue began around 2 AM, with affected devices logging fatal DNS client errors and rebooting repeatedly. The bug impacts a wide range of Cisco switch models, including CBS250, CBS350, Catalyst C1200, SG350, SG350X, and SG550X series. Administrators have discovered temporary workarounds, such as disabling DNS resolution or SNTP time synchronization.

Timeline

  1. 08.01.2026 22:40 1 articles · 23h ago

    Cisco Switches Experience Reboot Loops Due to DNS Client Bug

    Starting at approximately 2 AM, multiple Cisco switch models began experiencing reboot loops due to a DNS client bug. The bug causes the DNS client service to treat DNS lookup failures as fatal errors, leading to repeated reboots. Administrators have discovered temporary workarounds, such as disabling DNS resolution or SNTP time synchronization.

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Information Snippets

  • The bug causes the DNS client service to treat DNS lookup failures as fatal errors, leading to repeated reboots.

    First reported: 08.01.2026 22:40
    1 source, 1 article
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  • Affected switches log fatal errors before rebooting, with messages indicating failures to resolve 'www.cisco.com' and NTP time servers.

    First reported: 08.01.2026 22:40
    1 source, 1 article
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  • The reboot cycle repeats every few minutes, severely disrupting network operations.

    First reported: 08.01.2026 22:40
    1 source, 1 article
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  • Administrators have reported that disabling DNS resolution or SNTP time synchronization stops the reboot loops.

    First reported: 08.01.2026 22:40
    1 source, 1 article
    Show sources