Grading Checklist: Jumbo Frames Enabled But Some Paths Failing

• Identified that jumbo frames require end-to-end MTU consistency on every device in the path
• Used ping with large payload (-s 8972) and DF bit to test path MTU per hop
• Identified the specific switch or link segment that does not support jumbo frames
• Checked MTU settings on server NICs, switch access ports, and switch uplinks
• Explained why small packets work (below 1500 MTU) but large ones fail
• Noted that DF bit prevents fragmentation, causing silent black-holing
• Proposed fix: enable jumbo frames on the offending switch or adjust server MTU down
• Discussed PMTUD (Path MTU Discovery) and why it may not help if ICMP is blocked
• Mentioned checking switch hardware capabilities (some models have max MTU < 9000)
• Recommended systematic hop-by-hop MTU testing methodology
• Considered the impact on TCP MSS negotiation and throughput
• Warned about needing to coordinate MTU changes with all connected devices