Keyword Alternatives

Most networking professionals know some of the more commonly used TCP port numbers, and maybe a few UDP port numbers. Fewer could say what the ICMP type is for a ping or a destination unreachable, much less what the ICMP codes are for destination unreachable types. Beginning with IOS 10.3, access lists can be configured with keywords in place of many port, type, or code numbers. Using keywords, the access lists 110 and 111 from Figure B.10 are:

access-list 110 permit tcp any establishedaccess-list 110 permit tcp any host eq smtpaccess-list 110 permit tcp eq telnetaccess-list 110 permit udp host eq tftpaccess-list 110 permit udp any host eq domain ...

Get Routing TCP/IP, Volume I (CCIE Professional Development) now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.