In my company we've been investigating 1Gbps ethernet link between Cisco switches having only 150 kbps data rate.
It was a big ISP with engineers who could decipher IP packets from screen hex dump in their mind (I shit you not) and best Cisco support money can buy.
After few weeks it turned out that disabling auto speed negotiation and forcing 1G rate fixed the issue. And yes - all interfaces claimed that it was always 1G negotiated.
In my company we've been investigating 1Gbps ethernet link between Cisco switches having only 150 kbps data rate.
It was a big ISP with engineers who could decipher IP packets from screen hex dump in their mind (I shit you not) and best Cisco support money can buy.
After few weeks it turned out that disabling auto speed negotiation and forcing 1G rate fixed the issue. And yes - all interfaces claimed that it was always 1G negotiated.