Reference Guide

You can set this duration or interval for which the TCP connection waits to be established to a
significantly high value to prevent the device from moving into an out-of-service condition or becoming
unresponsive during a SYN flood attack that occurs on the device. You can set the wait time to be 10
seconds or lower. If the device does not contain any BGP connections with the BGP neighbors across
WAN links, you must set this interval to a higher value, depending on the complexity of your network and
the configuration attributes.
To configure the duration for which the device waits for the ACK packet to be sent from the requesting
host to establish the TCP connection, perform the following steps:
1. Define the wait duration in seconds for the TCP connection to be established.
CONFIGURATION mode
Dell(conf)#ip tcp reduced-syn-ack-wait <9-75>
You can use the no ip tcp reduced-syn-ack-wait command to restore the default behavior,
which causes the wait period to be set as 8 seconds.
2. View the interval that you configured for the device to wait before the TCP connection is attempted
to be established.
EXEC mode
Dell>show ip tcp reduced-syn-ack-wait
Enabling Directed Broadcast
By default, Dell Networking OS drops directed broadcast packets destined for an interface. This default
setting provides some protection against denial of service (DoS) attacks.
To enable Dell Networking OS to receive directed broadcasts, use the following command.
• Enable directed broadcast.
INTERFACE mode
ip directed-broadcast
To view the configuration, use the show config command in INTERFACE mode.
Resolution of Host Names
Domain name service (DNS) maps host names to IP addresses. This feature simplifies such commands as
Telnet and FTP by allowing you to enter a name instead of an IP address.
Dynamic resolution of host names is disabled by default. Unless you enable the feature, the system
resolves only host names entered into the host table with the ip host command.
The following sections describe DNS and the resolution of host names.
• Enabling Dynamic Resolution of Host Names
• Specifying the Local System Domain and a List of Domains
• Configuring DNS with Traceroute
In the release 9.4.(0.0), the Name server, Domain name, and Domain list are VRF specific. The maximum
number of Name servers and Domain lists per VRF is six.
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IPv4 Routing