Internet Speed
Internet Speed
This appears to be an ISP problem since the same speed is experienced across all devices in our network.
Everything seems fine. Your 100Mbps plan isn't reaching its full potential because you're only getting 80Mbps. This might be influenced by the service type and network traffic levels. All internet providers offer plans that are already used up, so if many users access the same connection at once, bandwidth gets restricted. If you're using a cable or DSL connection, age and distance from the provider's central hub can also affect performance.
Are you certain? Having an IP across multiple network cards isn't typical unless they're configured with trunking. This would cause an IP conflict, likely halting all devices or randomly permitting only one to operate. Stick with the faster option—it shouldn't affect performance.