The "established" keyword is used to indicate an established connection for TCP protocol. An established connection can be considered as the TCP traffic originating inside your network, not from an external network.

This means that the packets belong to an existing connection if the Transmission Control Protocol (TCP) segment has the Acknowledgment (ACK) or Reset (RST) bit set.

Example:

Router03(config)#access-list 102 permit tcp any any eq www established

 

Related Topics...

• Introduction to Access Control Lists (ACL)

• Standard Access Control Lists (ACLs)

• Where should a Standard Access Control List (ACL) be placed

• Access Control List (ACL) - Wildcard Masks

• How to create and configure Standard Access Control Lists (ACLs)

• Extended Access Control Lists (ACLs)

• Where should an Extended Access Control List (ACL) be placed

• Extended Access Control List (ACL) - Operators

• Extended Access Control List (ACL) - TCP and UDP port numbers and names

• Extended Access Control List (ACL)- established Keyword

• How to create and configure Access Control Lists (ACLs) for vty lines (telnet and ssh)

• Named Access Control Lists (ACLs)

• How to create and configure Standard Named Access Control Lists (ACLs)

• How to create and configure Extended Named Access Control List (ACL)

• How to edit a Named Access Control List (ACL) on router