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How to manually set NIC speed

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I have network performance problems (many output errors or collisions) on one of the network interfaces.


These problems might be caused by a failed network speed negotiation. Some network adapters, especially older devices from Cisco, are known for being unreliable when negotiating network speed automatically.

It is crucial to have the same settings on the interfaces on both sides of the cable, this is on the host and on the switch!

To confirm the assumption, check the output of netstat -in. Specifically look for errors and collisions, like in the following sample output:

> netstat -in
> Name Mtu Net/Dest Address Ipkts Ierrs Opkts Oerrs Collis Queue

> ce0 1500 2707133478 25 2895422910 142310052 182856975 0

Force an interface to a fixed speed

Here is how to force an interface to a fixed speed, e.g. to 100 MBit Full Duplex instead of auto-negotiate:

If the interface type is supported, it is possible to set the nicspeed in the Configuration Center under "System Setup" > "Nodes" separately per interface. Just find the optimal value in the "Speed Mode" drop-down list of each configuration block ("Management settings", "Back-end settings" and "External network interfaces").

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