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sh mac-address-table aged-out before aging-time

I continuously "show mac-address-table" and sometimes the mac-address disappear for few seconds(both vlan 192,189 simultaneously) and come up again eventhough the port never go down.

The switch is Catalyst 6509 with 12.2(18).SXD

see the log below:

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

lks-aggr6500-1#sh mac-address-table aging-time

Vlan Aging Time

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

Global 900

no vlan age other than global age configured

lks-aggr6500-1#sh mac-address-table dynamic vlan 192

Legend: * - primary entry

age - seconds since last seen

n/a - not available

vlan mac address type learn age ports

------+----------------+--------+-----+----------+--------------------------

* 192 0000.4cd6.5315 dynamic Yes 10 Po1

* 192 0000.4cd6.5302 dynamic Yes 10 Po1

* 192 0050.d176.b081 dynamic Yes 10 Fa3/4

lks-aggr6500-1#sh mac-address-table dynamic vlan 189

Legend: * - primary entry

age - seconds since last seen

n/a - not available

vlan mac address type learn age ports

------+----------------+--------+-----+----------+--------------------------

* 189 00e0.fc80.164a dynamic Yes 80 Gi1/2

* 189 00e0.fc80.1649 dynamic Yes 140 Gi1/2

* 189 00e0.fc81.6174 dynamic Yes 5 Gi1/2

* 189 00e0.fc81.6176 dynamic Yes 100 Gi1/2

* 189 00e0.fc80.1b47 dynamic Yes 5 Gi1/2

* 189 00e0.fc81.617d dynamic Yes 35 Gi1/2

* 189 00e0.fc81.617b dynamic Yes 110 Gi1/2

* 189 00e0.fc81.616a dynamic Yes 25 Gi1/2

* 189 00e0.fc81.616f dynamic Yes 250 Gi1/2

* 189 00e0.fc80.165c dynamic Yes 100 Gi1/2

* 189 0050.d176.b081 dynamic Yes 5 Fa3/4

* 189 00e0.fc81.6196 dynamic Yes 105 Gi1/2

* 189 00e0.fc84.66fe dynamic Yes 55 Po1

* 189 00e0.fc80.1b73 dynamic Yes 60 Gi1/2

* 189 00e0.fc80.1b72 dynamic Yes 130 Gi1/2

* 189 00e0.fc81.614b dynamic Yes 120 Gi1/2

* 189 00e0.fc80.1b71 dynamic Yes 140 Gi1/2

* 189 00e0.fc80.1b74 dynamic Yes 275 Gi1/2

* 189 00e0.fc81.6188 dynamic Yes 195 Gi1/2

* 189 00e0.fc80.1b61 dynamic Yes 110 Gi1/2

* 189 0030.f1a9.98a1 dynamic Yes 175 Gi1/2

* 189 00e0.fc80.1b6e dynamic Yes 35 Gi1/2

lks-aggr6500-1#sh mac-address-table dynamic vlan 192

Legend: * - primary entry

age - seconds since last seen

n/a - not available

vlan mac address type learn age ports

------+----------------+--------+-----+----------+--------------------------

* 192 0000.4cd6.5302 dynamic Yes 0 Po1

lks-aggr6500-1#sh mac-address-table dynamic vlan 189

Legend: * - primary entry

age - seconds since last seen

n/a - not available

vlan mac address type learn age ports

------+----------------+--------+-----+----------+--------------------------

No entries present.

lks-aggr6500-1#sh mac-address-table dynamic vlan 192

Legend: * - primary entry

age - seconds since last seen

n/a - not available

vlan mac address type learn age ports

------+----------------+--------+-----+----------+--------------------------

* 192 0000.4cd6.5302 dynamic Yes 0 Po1

lks-aggr6500-1#sh mac-address-table dynamic vlan 189

Legend: * - primary entry

age - seconds since last seen

n/a - not available

vlan mac address type learn age ports

------+----------------+--------+-----+----------+--------------------------

No entries present.

3 REPLIES
Silver

Re: sh mac-address-table aged-out before aging-time

Issue the command "show mac-address-table count", repeat that for the time to see the addresses increase or being reset.

If you run Per-VLAN Rapid STP for instance your mac-addres-table could be flushed due to a TCN BPDU.

HTH

Leon

* Please rate useful posts.

Bronze

Re: sh mac-address-table aged-out before aging-time

Leon is correct. To add to his comments if you’re not running RSTP the TCNs can be more prevalent than may you know.

With standard STP whenever an interface transitions from up to down a TCN is generated. Spanning-Tree portfast can be configured on user interfaces to eliminate this. But if you’re network is utilizing RSTP, I believe, a mechanism similar to portfast is inherent in RSTP.

If TCNs are causing this, here’s a document that shows you how to trace TCNs through the network.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094797.shtml#tnc

Ryan

Silver

Re: sh mac-address-table aged-out before aging-time

Hi Ryan,

The command displayed in your document is related to CatOS - had some trouble there in the past. The command that is most simular is "show spanning-tree vlan detail".

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