Cisco Cisco Packet Data Interworking Function (PDIF)
Firewall-and-NAT Policy Configuration Mode Commands
▀ firewall tcp-syn-flood-intercept
▄ Command Line Interface Reference, StarOS Release 16
4992
firewall tcp-syn-flood-intercept
This command configures TCP SYN intercept parameters for protection against TCP SYN flooding attacks.
Important:
In release 8.0, this configuration is available in the ACS Configuration Mode. In release 8.1, for
Rulebase-based Stateful Firewall configuration, this configuration is available in the ACS Rulebase Configuration
Mode. In release 8.3, this configuration is available in the ACS Rulebase Configuration Mode.
Mode. In release 8.3, this configuration is available in the ACS Rulebase Configuration Mode.
Product
PSF
Privilege
Security Administrator, Administrator
Mode
Exec > ACS Configuration > Firewall-and-NAT Policy Configuration
active-charging service service_name > fw-and-nat policy policy_name
Entering the above command sequence results in the following prompt:
[local]host_name(config-fw-and-nat-policy)#
Syntax
firewall tcp-syn-flood-intercept { mode { none | watch [ aggressive ] } | watch-timeout
intercept_watch_timeout }
intercept_watch_timeout }
default firewall tcp-syn-flood-intercept { mode | watch-timeout }
default
Configures the default settings for SYN Flood DoS protection.
mode { none | watch [ aggressive ] }
Specifies the TCP SYN flood intercept mode:
none
: Disables the TCP SYN Flood Intercept feature.
watch
: Configures TCP SYN flood intercept feature in watch mode. The Stateful Firewall passively
watches to see if TCP connections become established within a configurable interval. If connections
are not established within the timeout period, the Stateful Firewall clears the half-open connections
by sending RST to TCP client and server. The default watch-timeout for connection establishment is
30 seconds.
are not established within the timeout period, the Stateful Firewall clears the half-open connections
by sending RST to TCP client and server. The default watch-timeout for connection establishment is
30 seconds.
aggressive
: Configures TCP SYN flood Intercept or Watch feature for aggressive behavior. Each
new connection request causes the oldest incomplete connection to be deleted. When operating in
watch mode, the watch timeout is reduced by half. If the watch-timeout is 30 seconds, under
aggressive conditions it becomes 15 seconds. When operating in intercept mode, the retransmit
timeout is reduced by half (i.e. if the timeout is 60 seconds, it is reduced to 30 seconds). Thus the
amount of time waiting for connections to be established is reduced by half (i.e. it is reduced to 150
seconds from 300 seconds under aggressive conditions).
watch mode, the watch timeout is reduced by half. If the watch-timeout is 30 seconds, under
aggressive conditions it becomes 15 seconds. When operating in intercept mode, the retransmit
timeout is reduced by half (i.e. if the timeout is 60 seconds, it is reduced to 30 seconds). Thus the
amount of time waiting for connections to be established is reduced by half (i.e. it is reduced to 150
seconds from 300 seconds under aggressive conditions).
Default:
none