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CCNA Data Center DCICN 640-911 Official Cert Guide by Chad Hintz, Wendell Odom

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Matching TCP and UDP Port Numbers

Cisco Nexus ACLs can also examine parts of the TCP and UDP headers, particularly the source and destination port number fields. The port numbers identify the application that sends or receives the data.

The most useful ports to check are the well-known ports used by servers. For example, web servers use well-known port 80 by default. Figure 22-6 shows the location of the port numbers in the TCP header, following the IP header.

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Figure 22-6 IP Header, Followed by a TCP Header and Port Number Fields

When a Cisco Nexus ACL command includes either the tcp or udp keyword, that command can optionally reference the ...

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