Diagnostic Tools; Overview; The Ping Command - D-Link NetDefendOS User Manual

2.6. Diagnostic Tools

2.6.1. Overview

When troubleshooting network problems, NetDefendOS provides an assortment of tools to help
with problem resolution.
The section describes some of the most important troubleshooting tools available to the
administrator. Most of these are used as CLI commands.

2.6.2. The ping Command

The combination of the ICMP echo request and echo reply messages are known as ping. They
provide a simple diagnostic tool to find out if a host is reachable. In the NetDefendOS CLI, the
ping command provides this feature.
In its simplest form, the CLI command to ping a remote IP address takes the form:
gw-world:/> ping <ipaddress>
For example, to ping the IPv4 address 10.6.58.10:
gw-world:/> ping 10.6.58.10
Sending 1 4-byte ICMP ping to 10.6.58.10 from 192.168.3.20
using PBR table "main"
ICMP Reply from 192.168.1.1
Ping Results:
Here, the RTT is the round trip time for the ICMP echo request and reply messages. The TTL value
is the Time To Live which is a hop counter. The initial TTL value is set by the sender and
decremented by each router passed. When it reaches zero, the packet is discarded preventing
packets from circulating forever.
This basic form of the ping command can also be used in the NetDefendOS Web Interface by
going to: Status > Tools > Ping.
Choosing the Routing Table
By default, the outgoing source interface for ICMP ping is chosen by performing a lookup of the
destination IP address in the main routing table. This can be overridden with the -pbr option in
order to specify which routing table to use for the lookup. For example, if the routing table
my_routing_table is to be used, the command would be:
gw-world:/> ping 10.6.58.10 -pbr=my_routing_table -verbose
Sent: 1, Received:1, Avg RTT: 10.0 ms
Note: The -pbr option cannot be used with the -srcif option
The -pbr option cannot be used with packet simulation using the -srcif option described
later. This is because the routing table lookup for the outgoing interface is not relevant
when simulating incoming packets.
Chapter 2: Management and Maintenance
seq=0 time=<10 ms
118
TTL=128