求助题库的一道题

hechaoqian

Which of these is true regarding the configuration and application of port access control lists?


A. PACLs can be applied in the inbound or outbound direction of a Layer 2 physical interface.
B. At Layer 2, a MAC address PACL will take precedence over any existing Layer 3 PACL.
C. When you apply a port ACL to a trunk port, the ACL filters traffic on all VLANs present on the trunk port.
D. PACLs are not supported on EtherChannel interfaces.

答案是c
我觉得a也是正确的，prot acl可以用在二层接口的出和入方向。b也正确。二层pacl比三层pacl优先。不知道我哪里理解错了

rogerxyz

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/vacl.pdf
第49-3頁第二行
A Layer 2 port is a physical LAN or trunk port that belongs to a VLAN. Port ACLs are applied only on
the ingress traffic.

allencheng

A 是错的，B 我还没查到。

allencheng

答案B： 应该说是先检查PACL, 再检查3层的ACL。只是顺序上的先后而已。并不能说只要查了2层的就不要查3层的了。