Symptoms: Serial-over-LAN Output Garbled

• A headless Supermicro server in a remote colo is managed exclusively via IPMI Serial-over-LAN (SOL).
• When connecting via ipmitool sol activate, the output is garbled: random characters, misaligned text, and binary fragments.
• Occasionally a few readable characters appear, suggesting the serial data is present but corrupted.
• The server is running and responding to network pings and SSH; only SOL is broken.
• SSH access is currently available, but the team needs SOL working for BIOS/bootloader access during troubleshooting.
• The BIOS serial console redirection was configured during initial setup 2 years ago and worked previously.
• The issue started after a recent OS upgrade from RHEL 7 to RHEL 8.
• The BIOS firmware has not been changed.
• GRUB menu is also garbled via SOL, but the system boots normally.