Addendum

Traceroute works by sending packets with gradually increasing TTL value, starting with TTL value = 1. The
first router receives the packet, decrements the TTL value and drops the packet because it then has a TTL
value of zero. The router sends an ICMP Time Exceeded message back to the source. The next set of
packets are given a TTL value of 2; therefore, the first router forwards the packets, but the second router
drops them and replies with ICMP Time Exceeded. With such a progressive pattern, the traceroute
application uses the returned ICMP Time Exceeded messages to build a list of routers that packets
traverse, until the destination is reached and returns an ICMP Echo Reply message.
On Unix-based operating systems, the traceroute utility uses User Datagram Protocol (UDP) datagrams
by default, with destination port numbers ranging from 33434 to 33534.
ip icmp source-interface
Enable the ICMP error and unreachable messages to be sent with the source interface IP address, such as
the loopback address, instead of the hops of the preceding devices along the network path to be used for
easy debugging and diagnosis of network disconnections and reachability problems with IPv4 packets.
This functionality is supported on the S4810, S4820T, S6000, Z9000, and MXL platforms.
Syntax
ip icmp source-interface interface
Parameters
interface Enter one of the following keywords and slot/port or number
information:
• For a Management Ethernet interface, enter the keyword
managementethernet.
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 configured 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.
IPv4 Routing
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