Linux Server / Networking, SSH & Web Services
Check interface MTU when a server works for small requests only
A tunnel or overlay path can fail for larger packets while basic reachability works. Record the interface's actual MTU and path context.
Environment and inputs: Linux server baseline · Ubuntu 24.04 LTS / RHEL 9-style systems. Use the specified distribution, init system and installed tool; service names, privileges and supported options can differ.
Start with this check
Confirm the host, shell and access role. Replace sample names, paths, domains and interfaces with approved targets. These are diagnostic commands; assess policy and workload impact before making changes.
ip link show dev ens3Read the result
Replace ens3 with the intended interface. The output reports local MTU and link attributes, not the full path MTU to every destination.
Resolve and verify
Compare the tunnel overhead and approved network design with controlled packet-size and application tests. Make a targeted supported MTU correction after confirming the failure mode.
Before changing production
Do not reduce MTU globally based on one timeout; blocked diagnostic traffic can mimic a size issue.