Reference Guide

NOTE: When you configure the capability to enable
the loopback IP address to be sent for easy
debugging and diagnosis (IP addresses of the devices
for which the ICMP source interface is configured),
the source IP address of the outgoing ICMP error
message is modified, although the packets are not
sent out using the configured interface. Because the
management interface is configurable only without
any parameters such as the IP address, it is treated to
the management interface of the primary unit or the
existing unit.
• For a Loopback interface, enter the keyword loopback.
The range is from 0 to 16383.
• For a 1-Gigabit Ethernet interface, enter the keyword
GigabitEthernet.
• For a Port Channel interface, enter the keywords port-
channel then a number. The range is from 1 to 128.
• For a 10-Gigabit Ethernet interface, enter the keyword
TenGigabitEthernet.
• For a 40-Gigabit Ethernet interface, enter the keyword
fortyGigE.
• For a VLAN interface, enter the keyword vlan. The range
is from 1 to 4094.
Defaults Not configured.
Command
Modes
CONFIGURATION
Command
History
Version 9.3(0.0) Introduced on the S4810, S4820T, S6000, and Z9000
platforms.
Usage
Information
You can enable the mechanism to configure the source or the originating interface
from which the packet (the device that generates the ICMP error messages) is
received by the switch to send the loopback address instead of its source IP
address to be used in the ICMP unreachable messages and in the traceroute
command output. The loopback address must be unique in a particular domain.
In network environments that contain a large number of devices, ranging up to
thousands of systems, and with each device configured for equal-cost multipath
(ECMP) links, you cannot effectively and optimally use the traceroute and ping
applications to examine the network reachablity and identify any broken links for
diagnostic purposes. In such cases, if the reply that is obtained from each hop on
the network path contains the IP address of the adjacent, neighboring interface
from which the packet is received, it is difficult to employ the ping and traceroute
utilites. You can enable the ICMP unreachable messages to contain the loopback
address of the source device instead of the previous hop's IP address to be able to
easily and quickly identify the device and devices along the path because the DNS
server maps the loopback IP address to the hostname and does not translate the IP
address of every interface of the switch to the hostname.
860
IPv4 Routing