78
C
HAPTER
4: M
ANAGING
D
EVICE
S
ECURITY
■
Select from List
— Selects a protocol from a list by which packets
are matched to the rule.
■
Protocol ID
— Adds user-defined protocols by which packets are
matched to the rule. Each protocol has a specific protocol number
which is unique. The possible field range is
0-255
.
■
Source Port
— Enables creating an ACL based on a specific protocol.
■
Any
— Enables creating an ACL based on any protocol.
■
Destination Port
— Defines the destination port that is matched to
packets. Enabled only when TCP or UDP are selected in the Protocol
list.
■
Any
— Enables creating an ACL Based on any protocol.
■
TCP Flags
— If checked, enables configuration of TCP flags matched
to the packet. The possible fields are:
■
Urg
— Urgent pointer field significant. The urgent pointer points to
the sequence number of the octet following the urgent data.
■
Ack
— Acknowledgement field significant. The acknowledgement
field is the byte number of the next byte that the sender expects to
receive from the receiver.
■
Psh
— Push (send) the data as soon as possible, without buffering.
This is used for interactive traffic.
■
Rst
— Reset the connection. This invalidates the sequence numbers
and aborts the session between the sender and receiver.
■
Syn
— Synchronize Initial Sequence Numbers (ISNs). This is used to
initialize a new connection.
■
Fin
— Finish. This indicates there is no more data from the sender.
This marks a normal closing of the session between the sender and
receiver.
For each TCP flag, the possible field values are:
■
Set
— Enables the TCP flag.
■
Unset
— Disables the TCP flag.
■
Don’t Care
— Does not check the packet’s TCP flag.