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why access switch has flapping lead another distribution layer switch has root guard blocking and unblocking log

martlee2
Cisco Employee
Cisco Employee

is it misconfiguration in Access Point's access switch or hacker attack from this switch?

 

many MATM-4-MACFLAP_NOTIF Host 0015.5dc1XXX VLAN 1 is flapping between port 1 and port 2

many MATM-4-MACFLAP_NOTIF Host 0015.5dc2XXX VLAN 1 is flapping between port 1 and port 2

many MATM-4-MACFLAP_NOTIF Host 0015.5dc3XXX VLAN 50 is flapping between port 1 and port 2

many MATM-4-MACFLAP_NOTIF Host 0015.5dc4XXX VLAN 50 is flapping between port 1 and port 2

 

last time we do not have these switch also meet the same issue about distribution layer switch have many ports down

 

last time someone mention a switch lost config, but today, i remember that the switch has reloaded and can be login again with radius, 

today i do not connect any notebook with this switch and just have configured radius setting for window NPS radius server and then reload, then

i have dinner and come back and after a while, last time's issue happen again. 

it seems port channel easy to have problem when abnormal traffic coming from access switch  result in down port in distribution layer switch

 

i wonder whether someone can hack through the switchport access mode port and send some broadcast message

1 Reply 1

petenixon
Level 3
Level 3

From that output and your description it looks like you have an STP issue as a result of misconfiguration somewhere.

Are your access points connected to switches with ports in access mode or trunk mode?

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