Enabling Icmp Mask Reply Messages - Cisco Catalyst 4500 Series Configuration Manual

Configuring ICMP
However, when Hot Standby Router Protocol (HSRP) is configured on an interface, ICMP Redirect
messages are disabled (by default) for the interface. For more information on HSRP, refer to the
following URL:
http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_hsrp_ps6350_TSD_Products_Confi
guration_Guide_Chapter.html
To enable the sending of ICMP Redirect messages if the Cisco IOS software is forced to resend a packet
through the same interface on which it was received, enter the following command in interface
configuration mode:
Command
Switch (config-if)# [no] ip redirects

Enabling ICMP Mask Reply Messages

Occasionally, network devices must know the subnet mask for a particular subnetwork in the
internetwork. To obtain this information, devices can send ICMP Mask Request messages. These
messages are responded to by ICMP Mask Reply messages from devices that have the requested
information. The Cisco IOS software can respond to ICMP Mask Request messages if the ICMP Mask
Reply function is enabled.
To have the Cisco IOS software respond to ICMP mask requests by sending ICMP Mask Reply
messages, enter the following command:
Command
Switch (config-if)# [no] ip mask-reply
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
8-14
Chapter 8 Checking Port Status and Connectivity
Purpose
Enables ICMP Redirect messages.
Use the no keyword to disable the ICMP Redirect
messages and reduce CPU usage.
Purpose
Enables response to ICMP destination mask requests.
Use the no keyword to disable this functionality.
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