3750 MAC Address Table

kalebkspkalebksp Member Posts: 1,033 ■■■■■□□□□□
I am labbing MAC flooding attacks on my 3750 and came across a seemingly weird issue. When the table is full and I can see unicast frames on ports they weren't intended for 'show mac address-table count' still shows space for 40 more addresses. Are there some "slots" reserved on 3750s? I thought they might be for static entries, but after adding a few statics it seems that is not the case. I tried the same thing on a 3550 and it shows no address space available.

I upgraded to the latest IOS (12.2(53)SE2) with the same results.
Switch#show mac address-table count

Mac Entries for Vlan 1:
Dynamic Address Count  : 5960
Static  Address Count  : 0
Total Mac Addresses    : 5960

Total Mac Address Space Available: 40

Any insight is appreciated.


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