3com 2500 User Guide

ICMP performs these tasks:

■

Tests whether nodes can be reached (ICMP Echo Request and 
ICMP Echo Reply) — A host or gateway sends an ICMP echo request 
to a specified destination. If the destination receives the echo request, 
it sends an ICMP echo reply to the sender. This process tests whether 
the destination is reachable and responding and verifies that the 
network’s transport hardware and software are working. The 

 

command is frequently used to invoke this process.

■

Creates more efficient routing (ICMP Redirect) — Often the host 
route configuration specifies the minimum possible routing data that 
is needed to communicate (for example, the address of a single 
router). The host relies on routers to update its routing table. In the 
process of routing packets, a router may detect that a host is not using 
the best route. The router sends an ICMP redirect to this host, 
requesting that the host use a different gateway when it sends 
packets to a destination. The host then sends packets to that 
destination using the new route.

■

Informs sources that a packet has exceeded its allocated time to 
exist within the network (ICMP Time Exceeded)

CoreBuilder Extended Switching software supports classical IP routing 
over ATM ARP in an ATM network. The Classical IP over ATM model uses 
Logical IP Subnetworks (LISs) to forward packets within the network 
environment. 

A LIS is a group of IP nodes that belong to the same subnetwork and are 
directly connected to a single ATM network. When you add a node to a 
LIS through the Administration Console IP interface menu, you define its 
IP address, subnet mask, and the address of an ATM ARP server that 
supports it.