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Suspicious Mac Address Entires and Mac address table inconsistencies

Network Connectivity:

Cisco 6880 Layer 3 Switch Management Interface is connected to downstream Cisco 2960s Layer 2 switch to the Int G1/0/7 over a access Vlan 8


Issues:

1. Suspicious MAC-addresses are seen on the downstream Cisco 2960s Layer 2 switch coming from Cisco 6880 switch but when we log onto Cisco 6880 we do not see the mac addresses
2. These suspicious MAC-addresses are changing the Mac address count of Vlan 8 every 4 secs for ex 1st it will show count of 143 ,2nd count will be 159 ,3rd count will be 153 and so on causing mac table inconsistency on Cisco 2960s and all other downstream devices
3. Vendor of the Mac address is unknown when we do a Mac vendor lookup on Internet

 

Logs:

IDCNET_SW_INT_01#sh mac address-table (Cisco 2960s)

Legend: * - primary entry
age - seconds since last seen
n/a - not available
S - secure entry
R - router's gateway mac address entry
D - Duplicate mac address entry

Displaying entries from active supervisor:

vlan mac address type learn age ports
----+----+---------------+-------+-----+----------+-----------------------------
* 2 0000.0000.fe00 dynamic Yes 0 Po11
* 2 0000.0000.fe01 dynamic Yes 0 Po12
* 2 001c.7f3f.0531 dynamic Yes 0 Po12
* 2 001c.7f60.0431 dynamic Yes 0 Po11
R N/A 0008.e3ff.fc28 static No - Router
* 2 f4ce.46ba.d47e dynamic Yes 0 Te1/5/7
R N/A 0008.e3ff.fc28 static No - Router
* 2 0008.e0ff.fc28 dynamic Yes 0 Po11
R N/A 0008.e3ff.fc28 static No - Router
R 2 0008.e3ff.fc28 static No - Router

IDCNET_SW_IDMZ_02#sh mac address-table (Cisco 6880)
Mac Address Table
-------------------------------------------

Vlan Mac Address Type Ports
8 0036.10cf.0009 DYNAMIC Gi1/0/7
8 0036.119c.0009 DYNAMIC Gi1/0/7
8 0036.13a7.0009 DYNAMIC Gi1/0/7
8 0036.309d.0009 DYNAMIC Gi1/0/7
8 0036.39af.0009 DYNAMIC Gi1/0/7
8 0036.3fbc.0009 DYNAMIC Gi1/0/7
8 0036.5827.0009 DYNAMIC Gi1/0/7
8 0036.6886.0009 DYNAMIC Gi1/0/7
8 0036.81dc.0009 DYNAMIC Gi1/0/7
8 0036.8a05.0009 DYNAMIC Gi1/0/7
8 0036.917d.0009 DYNAMIC Gi1/0/7
8 0036.93e0.0009 DYNAMIC Gi1/0/7
8 0036.aa47.0009 DYNAMIC Gi1/0/7
8 0036.abd3.0009 DYNAMIC Gi1/0/7
8 0036.b777.0009 DYNAMIC Gi1/0/7
8 0036.be01.0009 DYNAMIC Gi1/0/7
8 0036.dbcf.0009 DYNAMIC Gi1/0/7
8 0036.decc.0009 DYNAMIC Gi1/0/7
8 0036.e41b.0009 DYNAMIC Gi1/0/7
8 0036.eadc.0009 DYNAMIC Gi1/0/7
8 0036.fb08.0009 DYNAMIC Gi1/0/7
8 0036.fc16.0009 DYNAMIC Gi1/0/7
8 0036.fe3b.0009 DYNAMIC Gi1/0/7
8 004c.0e84.0009 DYNAMIC Gi1/0/7
8 004c.6dc7.0009 DYNAMIC Gi1/0/7
8 004c.7aac.0009 DYNAMIC Gi1/0/7
8 004c.8df8.0009 DYNAMIC Gi1/0/7
8 004c.a348.0009 DYNAMIC Gi1/0/7
8 004c.a57a.0009 DYNAMIC Gi1/0/7
8 004c.bf7d.0009 DYNAMIC Gi1/0/7
8 004c.c801.0009 DYNAMIC Gi1/0/7
8 004c.e6d8.0009 DYNAMIC Gi1/0/7
8 0062.13f4.0009 DYNAMIC Gi1/0/7
8 0062.2399.0009 DYNAMIC Gi1/0/7
8 0062.3a79.0009 DYNAMIC Gi1/0/7
8 0062.4ee7.0009 DYNAMIC Gi1/0/7
8 0062.87d8.0009 DYNAMIC Gi1/0/7
8 0062.9112.0009 DYNAMIC Gi1/0/7
8 0062.9607.0009 DYNAMIC Gi1/0/7
8 0062.96e1.0009 DYNAMIC Gi1/0/7
8 0062.a287.0009 DYNAMIC Gi1/0/7
8 0062.b92f.0009 DYNAMIC Gi1/0/7
8 0078.4485.0009 DYNAMIC Gi1/0/7
8 0078.46ec.0009 DYNAMIC Gi1/0/7
8 0078.852e.0009 DYNAMIC Gi1/0/7
8 0078.98fa.0009 DYNAMIC Gi1/0/7
8 0078.9f84.0009 DYNAMIC Gi1/0/7
8 0078.a8d7.0009 DYNAMIC Gi1/0/7
8 0078.bd45.0009 DYNAMIC Gi1/0/7
8 0078.c683.0009 DYNAMIC Gi1/0/7
8 0078.cca2.0009 DYNAMIC Gi1/0/7
8 0078.d57e.0009 DYNAMIC Gi1/0/7
8 0078.d640.0009 DYNAMIC Gi1/0/7
8 0078.dfdd.0009 DYNAMIC Gi1/0/7
8 0078.ec9f.0009 DYNAMIC Gi1/0/7
8 0078.fe5b.0009 DYNAMIC Gi1/0/7
8 008e.ad54.0009 DYNAMIC Gi1/0/7
8 008e.b931.0009 DYNAMIC Gi1/0/7
8 008e.bd6c.0009 DYNAMIC Gi1/0/7
8 008e.d2c8.0009 DYNAMIC Gi1/0/7
8 008e.d929.0009 DYNAMIC Gi1/0/7
8 00a4.13f9.0009 DYNAMIC Gi1/0/7
8 00a4.209e.0009 DYNAMIC Gi1/0/7
8 00a4.2848.0009 DYNAMIC Gi1/0/7
8 00a4.2a9f.0009 DYNAMIC Gi1/0/7
8 00a4.3466.0009 DYNAMIC Gi1/0/7
8 00a4.898e.0009 DYNAMIC Gi1/0/7
8 00a4.b249.0009 DYNAMIC Gi1/0/7
8 00a4.f665.0009 DYNAMIC Gi1/0/7
8 00ae.e41f.0009 DYNAMIC Gi1/0/7
8 00ba.0826.0009 DYNAMIC Gi1/0/7
8 00ba.14a0.0009 DYNAMIC Gi1/0/7
8 00ba.2aad.0009 DYNAMIC Gi1/0/7
8 00ba.4217.0009 DYNAMIC Gi1/0/7
8 00ba.55d8.0009 DYNAMIC Gi1/0/7
8 00ba.6cc6.0009 DYNAMIC Gi1/0/7
8 00ba.7550.0009 DYNAMIC Gi1/0/7
8 00ba.9134.0009 DYNAMIC Gi1/0/7
8 00ba.d74d.0009 DYNAMIC Gi1/0/7
8 00d0.0ae2.0009 DYNAMIC Gi1/0/7
8 00d0.0b42.0009 DYNAMIC Gi1/0/7
8 00d0.26df.0009 DYNAMIC Gi1/0/7
8 00d0.66ff.0009 DYNAMIC Gi1/0/7
8 00d0.7390.0009 DYNAMIC Gi1/0/7
8 00d0.b119.0009 DYNAMIC Gi1/0/7
8 00d0.c31e.0009 DYNAMIC Gi1/0/7
8 00e6.4c36.0009 DYNAMIC Gi1/0/7
8 00e6.4e4a.0009 DYNAMIC Gi1/0/7
8 00fc.d0df.0009 DYNAMIC Gi1/0/7

 

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