Dell PowerConnect 5212 System User's Manual page 78

You can clear a port's counters by clicking the Reset Counter button at the bottom of the Table page.
CLI Commands
The following table summarizes the equivalent CLI commands for items in the Statistics/Table page.
Command
show interfaces counters interface
clear counters interface
Example
Console#show interfaces counters ethernet 1/12
Ethernet 1/12
Iftable stats:
Octets input: 91248, Octets output: 343887
Unitcast input: 680, Unitcast output: 593
Discard input: 0, Discard output: 0
Error input: 0, Error output: 0
Usage
Statically configures a multicast router port
Clears statistics on an interface