Using The –T (Traceroute) Option; Figure C3-1. Overview Of Ping -T Actions - Bay Networks 5390 Administering

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Using the –t (traceroute) Option

The ping –t command sends only one ICMP Echo Request. This request, called the outbound packet,

contains an IP traceroute option and a traceroute hop count of zero. If an outbound packet crosses

routers on the path to its destination, each router increments the hop count by one, forwards the

packet, if possible, and returns a traceroute message to the originator (Figure C3-1 illustrates an

outbound packet that crosses two routers). This message indicates whether or not the packet was

forwarded. If so, the message contains the incremented hop count and information about the

outbound interface over which the packet was forwarded. If the packet could not be forwarded, the

router discards it, ping –t terminates, and the traceroute message contains zeros in place of interface

information.

If an outbound packet reaches its destination, the destination node sends an ICMP Echo Response,

called the return packet, to the router from which it received the outbound packet. The destination

node copies the traceroute option from the outbound packet to the return packet and sets the return

packet's hop count to zero. If the return packet passes through the routers in the path back to the

ping –t source, each router increments the hop count by one, forwards the packet, if possible, and

returns a traceroute message to the ping –t source (see Figure C3-1).

The traceroute message indicates whether or not the packet was forwarded. If so, the message

includes the incremented hop count and information about the interface over which the packet was

forwarded. If the packet could not be forwarded, the router discards it, ping –t terminates, and the

traceroute message contains zeros in place of interface information.

Figure C3-1. Overview of ping –t Actions

Outbound packet

Traceroute message caused by outbound packet

Return packet

Traceroute message caused by return packet

Using the CLI Commands