Configuring The Duration To Establish A Tcp Connection; Enabling Directed Broadcast; Resolution Of Host Names - Dell S4048–ON Configuration Manual

Configure the source to send the configured source interface IP address instead of using its front-end IP address in the ICMP
unreachable messages and in the traceroute command output. Use the ip icmp source-interface interface or the
ipv6 icmp source-interface interface commands in Configuration mode to enable the ICMP error messages to be
sent with the source interface IP address. This functionality is supported on loopback, VLAN, port channel, and physical interfaces
for IPv4 and IPv6 messages. feature is not supported on tunnel interfaces. ICMP error relay, PATH MTU transmission, and
fragmented packets are not supported for tunnel interfaces. The traceroute utilities for IPv4 and IPv6 list the IP addresses of the
devices in the hops of the path for which ICMP source interface is configured.

Configuring the Duration to Establish a TCP Connection

You can configure the duration for which the device must wait before it attempts to establish a TCP connection. Using this
capability, you can limit the wait times for TCP connection requests. Upon responding to the initial SYN packet that requests a
connection to the router for a specific service (such as SSH or BGP) with a SYN ACK, the router waits for a period of time for the
ACK packet to be sent from the requesting host that will establish the TCP connection.
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 commands such 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.
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IPv4 Routing