Configuring The Icmp Source Interface; Configuring The Duration To Establish A Tcp Connection; Enabling Directed Broadcast - Dell Force10 Z9000 Configuration Manual

Configuring the ICMP Source Interface

You can enable the ICMP error and unreachable messages to contain the configured IP address of the source device instead of the
previous hop's IP address. This configuration helps identify the devices along the path because the DNS server maps the loopback IP
address to the host name, and does not translate the IP address of every interface of the switch to the host name.
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

This functionality is supported on the Z9000 platform.
You can configure the amount of time 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
321
IPv4 Routing