第136题

UID: 64347

104.4最新的情人节版本 第136题，有疑惑，我觉得A是对的
在外网查了一下， 给出的解析如下！
What is valid reason for a switch to deny port access to new devices when port security is enabled?

A. The denied MAC addresses have already been learned or configured on another secure interface in the same VLAN.
B. The denied MAC address are statically configured on the port.
C. The minimum MAC threshold has been reached.
D. The absolute aging times for the denied MAC addresses have expired.

Answer: A

Explanation

A security violation occurs in either of these situations:

* When the maximum number of secure MAC addresses is reached on a secure port and the source MAC address of the ingress traffic is different from any of the identified secure MAC addresses, port security applies the configured violation mode.

* If traffic with a secure MAC address that is configured or learned on one secure port attempts to access another secure port in the same VLAN, applies the configured violation mode.

From the second statement we can figure out A is the correct answer. But for your information we will discuss other answers as well.
Answer B is not correct because we can’t configured which MAC address will be denied. We can only configure which MAC is allowed.
We can only configure the maximum MAC threshold, not the minimum threshold -> C is not correct.
The aging times are only configured for allowed MAC addresses, not for denied MAC -> D is correct.
For your information about aging time:
When the aging type is configured with the absolute keyword, all the dynamically learned secure addresses age out when the aging time expires
This is how to configure the secure MAC address aging type on the port:
Router(config-if)# switchport port-security aging type absolute
and configure the aging time (aging time = 120 minutes)
Router(config-if)# switchport port-security aging time 120
When this command is used, all the dynamically learned secure addresses age out when the aging time expires

UID: 69740

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