I have a cisco 3560 switch with 3 routers and 4 servers, and an uplink port connected to it, all in the same VLAN.
Until lately the uplink was a trunk port connected to another cisco switch, and configuration of the VLAN was made by the engineer of the backbone ISP.
A few days we changed backbone provider, the uplink port is now connected to another switch port via fiber, without any trunking. The other side are telling me that their switch port is learning a new mac for the port allocated to me. I believe what is happening is that all the mac addresses of my servers and routers are being forwarded plain to their port, and is worsening our network performance.
Any advice on how can a fix this? Possibly without a new router or a trunk, as I need to make changes soon. Can I forward just one mac to the outside switch?
Feedback is greatly appreciated!