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MAC table is not correct

Regarding my previous question - why 3750 can not be access from outside except from console. I just find something interesting, the MAC table does not have associated interface MAC address, here is the details, I'd like to know

1.what those first 20 MAC entries for?

2.There are a lot of traffic in this switch, is there any outrage if I reset MAC table?

3.why GigabitEthernet1/0/1 is in ARP table, but not in MAC table? this is layer 3 interface and has fixed IP assigned.

xy_3750-1#sh mac-

Mac Address Table


Vlan Mac Address Type Ports

---- ----------- -------- -----

All 0100.0ccc.cccc STATIC CPU

All 0100.0ccc.cccd STATIC CPU

All 0180.c200.0000 STATIC CPU

All 0180.c200.0001 STATIC CPU

All 0180.c200.0002 STATIC CPU

All 0180.c200.0003 STATIC CPU

All 0180.c200.0004 STATIC CPU

All 0180.c200.0005 STATIC CPU

All 0180.c200.0006 STATIC CPU

All 0180.c200.0007 STATIC CPU

All 0180.c200.0008 STATIC CPU

All 0180.c200.0009 STATIC CPU

All 0180.c200.000a STATIC CPU

All 0180.c200.000b STATIC CPU

All 0180.c200.000c STATIC CPU

All 0180.c200.000d STATIC CPU

All 0180.c200.000e STATIC CPU

All 0180.c200.000f STATIC CPU

All 0180.c200.0010 STATIC CPU

All ffff.ffff.ffff STATIC CPU

3 0007.e925.0c91 DYNAMIC Gi1/0/14

2 000e.0c5c.ac83 DYNAMIC Gi1/0/2

4 000e.0c5c.ad8d DYNAMIC Gi1/0/4

7 0001.4232.e671 DYNAMIC Gi1/0/8

7 0001.961f.71ed DYNAMIC Gi1/0/8

7 0002.1611.2dab DYNAMIC Gi1/0/8

7 0003.e339.bcf1 DYNAMIC Gi1/0/8

7 0009.4345.0830 DYNAMIC Gi1/0/8

7 0009.4345.08e4 DYNAMIC Gi1/0/8

7 0009.7ca3.28a4 DYNAMIC Gi1/0/8

7 0009.7ca3.2b1a DYNAMIC Gi1/0/8

7 000b.5fda.0b02 DYNAMIC Gi1/0/8

7 000c.3082.130c DYNAMIC Gi1/0/8

7 000c.3082.1928 DYNAMIC Gi1/0/8

7 000d.bd6d.7324 DYNAMIC Gi1/0/8

7 000e.3846.ac62 DYNAMIC Gi1/0/8

7 0012.0048.ee62 DYNAMIC Gi1/0/8

7 0012.0048.f472 DYNAMIC Gi1/0/8

7 00b0.643d.36c0 DYNAMIC Gi1/0/8

7 00b0.643d.36c1 DYNAMIC Gi1/0/8

7 00d0.ba80.2cc3 DYNAMIC Gi1/0/8

6 0002.b3a8.ab04 DYNAMIC Gi1/0/6

6 0004.42ff.02e4 DYNAMIC Gi1/0/6

6 0006.5b3e.bd99 DYNAMIC Gi1/0/6

6 0080.f948.0262 DYNAMIC Gi1/0/6

6 00c0.b792.573c DYNAMIC Gi1/0/6

6 00d0.9769.cec0 DYNAMIC Gi1/0/6

6 00d0.9769.cec1 DYNAMIC Gi1/0/6

8 0090.7f04.cfbd DYNAMIC Gi1/0/10

5 000e.0c5b.8235 DYNAMIC Gi1/0/16

Total Mac Addresses for this criterion: 50

xy_3750-1#sh arp

Protocol Address Age (min) Hardware Addr Type Interface

Internet x.y.z.65 1 0011.2047.441b ARPA GigabitEthernet1/0/1

Internet x.y.z.70 - 0013.194e.c7c1 ARPA GigabitEthernet1/0/1

Internet x.y.z.73 2 0011.2047.441c ARPA GigabitEthernet1/0/13

Internet x.y.z.78 - 0013.194e.c7c9 ARPA GigabitEthernet1/0/13

New Member

Re: MAC table is not correct


1. The 01-80-c2-00-00-00 to 01-80-c2-00-00-10 MAC addresses are used by the Spanning Tree Protocol and the Catalyst is always listening to this mac address range, so they are displayed as static entries on the MAC address table.

2. A temporary outage would result if you clean the mac address table, nothing really serious, but if critical applications are running then you better do it afterhours, but I see no need to do something like that.

3. The 'show ip arp' command only reflects MAC addresses learned by the switch itself, that is, traffic originating or terminating directly on the switch just like running the 'arp -a' command on a Windows PC.


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