Troubleshooting - Tag - Fryguy's Bloghttps://fryguy.net/tags/troubleshooting/Troubleshooting - Tag - Fryguy's BlogHugo -- gohugo.ioenThu, 13 Aug 2026 12:00:00 +0000MTU Path Test — Find Where a Path Silently Fragments, Hop by Hophttps://fryguy.net/2026/08/13/mtu-path-test-find-where-a-path-silently-fragments-hop-by-hop/Thu, 13 Aug 2026 12:00:00 +0000Fryguyhttps://fryguy.net/2026/08/13/mtu-path-test-find-where-a-path-silently-fragments-hop-by-hop/MTU problems are some of the most annoying things to troubleshoot in networking, because they’re usually silent. Small packets sail through fine, everything looks healthy, and then someone complains that a specific app is slow or hanging — and it turns out one link in the path, three hops in, has an MTU 8 bytes smaller than everyone assumed. GRE, IPsec, PPPoE, a VPN overlay, a jumbo-frame config that only got applied to half the path, a VLAN tag quietly adding 4 bytes nobody accounted for, or just two vendors defining and displaying “MTU” differently (L2 vs. L3, tagged vs. untagged) — any of these can quietly clip your effective MTU, and standard ping/traceroute won’t tell you where.

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