Command Reference Guide

SROS Command Line Interface Reference Guide Global Configuration Mode Command Set

ip firewall check syn-flood

Use the ip firewall check syn-flood command to enable the Secure Router OS stateful inspection firewall

to filter out phony TCP service requests and allow only legitimate requests to pass through. Use the no

form of this command to disable this feature.

Syntax Description

No subcommands.

Default Values

All

Secure Router OS

security features are disabled by default until the ip firewall command is issued at

the Global Configuration prompt. In addition, the SYN-flood check is disabled until the ip firewall check

syn-flood command is issued.

Command Modes

(config)# Global Configuration Mode

Functional Notes

SYN Flooding is a well-known denial of service attack on TCP-based services. TCP requires a three-way

handshake before actual communications begin between two hosts. A server must allocate resources to

process new connection requests that are received. A potential intruder is capable of transmitting large

amounts of service requests (in a very short period of time), causing servers to allocate all resources to

process the phony incoming requests. Using the ip firewall check syn-flood command configures the

Secure Router OS stateful inspection firewall to filter out phony service requests and allow only legitimate

requests to pass through.

Usage Examples

The following example enables the Secure Router OS syn-flood check:

(config)#ip firewall check syn-flood

Note

The Secure Router OS security features must be enabled (using the ip firewall command)

for the stateful inspection firewall to be activated.