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Beginner

Cisco CATALYST 9200 mac address learning

Hi,

I am new to this type of switch and installing the switch i came across the issue that the mac address table is not populated.

#SH MAC ADdress-table LEarning
Learning disabled on vlans:

 

Do you need how to activate mac learning which seems not activated by default ?

 

Thanks

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6 REPLIES 6
VIP Mentor

Re: Cisco CATALYST 9200 mac address learning

Hi
Its just command ---sh mac address-table
Not learning , learning is disabled by default , learning is disabled for IDS as a security feature
Beginner

Re: Cisco CATALYST 9200 mac address learning

Thanks for the reply.

Do you know the document for activating the mac learning on the switch please ? I cannot find the documentation for the security feature

 

Difficult to troubleshoot without access to the mac address table.

 

VIP Mentor

Re: Cisco CATALYST 9200 mac address learning

Its disabled on all most switches by default not just 9ks , 3ks and 4ks are the same , its protecting the switch you dont need it to troubleshoot layer 2 macs , you just use the command show mac address-table to see the full mac add table or show mac address-table address H.H.H

if you want to turn it on its per specific vlan --- mac address-table learning ?
vlan MAC Address table learning per VLAN


You could cause issues disabling it , its not really recommended

Disabling MAC Address Learning on an Interface or VLAN

By default, MAC address learning is enabled on all interfaces and VLANs on the router. You can control MAC address learning on an interface or VLAN to manage the available MAC address table space by controlling which interfaces or VLANs can learn MAC addresses. Before you disable MAC address learning, be sure that you are familiar with the network topology and the router system configuration. Disabling MAC address learning on an interface or VLAN could cause flooding in the network.

 

 

For the specific doc for your software release will be its config guide, there is a link to it where you download the image on the Cisco website , like example below

 

https://www.cisco.com/c/en/us/support/switches/catalyst-9200-r-series-switches/products-installation-and-configuration-guides-list.html

Beginner

Re: Cisco CATALYST 9200 mac address learning

Hi,

Thanks for the reply and it makes sense but on the switch.

SW_NETCENTRE_VNX_FRONTEND#sh mac address-table
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 0180.c200.0021 STATIC CPU
All ffff.ffff.ffff STATIC CPU
1 dc8c.37a4.48c7 STATIC Vl1
Total Mac Addresses for this criterion: 22

 

But I am not seeing other mac addresses while I have got the interfaces up on vlan 1 and operational for example.

The version  is 16.10.1.

 

 

 

 

 

 

 

 

 

VIP Mentor

Re: Cisco CATALYST 9200 mac address learning

Ok should be seeing dynamic but i dont think enabling learning will fix it as i havent got it enabled on 16.6.5 Everest MD or any other switch , your using and ED deployment if thats Gibraltar release 16.10.1 , you should use a star MD version there's less chance of bugs and issues


1#sh ver | i 16.6
Cisco IOS Software [Everest], Catalyst L3 Switch Software (CAT9K_IOSXE), Version 16.6.5, RELEASE SOFTWARE (fc3)
* 1 62 C9300-48P 16.6.5 CAT9K_IOSXE INSTALL
2 62 C9300-48P 16.6.5 CAT9K_IOSXE INSTALL
3 62 C9300-48P 16.6.5 CAT9K_IOSXE INSTALL
1#sh mac address-table learning
Learning disabled on vlans:
xar-b103uas01#sh mac address-table
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 0180.c200.0021 STATIC CPU
All ffff.ffff.ffff STATIC CPU
1 2c73.a03a.9bb5 DYNAMIC Po1
1 2c73.a03a.9bb7 DYNAMIC Po1
1 2c73.a03a.a635 DYNAMIC Po1
226 0077.8d3b.4775 STATIC Vl226



So you have another switch connected here with its MACs in the CAM table but there not being passed to the 9K switch ? is that right ?
Is the trunk fully formed and STP is no6t being blocked at layer 2 , just something to check
VIP Mentor

Re: Cisco CATALYST 9200 mac address learning

Could try this specific command too if you know a dynamic MAC on the network already and then try trace it at layer 2 see if its being blocked somewhere

sh mac address-table dynamic address b0b8.67ce.37e0
Mac Address Table
-------------------------------------------

Vlan Mac Address Type Ports
---- ----------- -------- -----
2144 b0b8.67ce.37e0 DYNAMIC Gi3/0/16
Total Mac Addresses for this criterion: 1

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