!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!
Success rate is 100 percent (100/100), round-trip min/avg/max = 2/2/3 ms
DGS-3610#
5.2 Traceroute Connectivity Test
The Traceroute command can be used to show all the gateways that the packet passes
through from the source to the destination. The Traceroute command is mainly used to
check the network connectivity and exactly locate the fault when the network fails.
One of the network transmission rules is that the number in the TTL field in the packet will
decrease by 1 every time when the packet passes through a gateway. When the number in
the TTL field is 0, the gateway will discard this packet and send an address unreachable
error packet to the source. According to this rule, the execution of the Traceroute command
is as follows: At first, it sends one packet with 1 as TTL to the destination address. The first
gateway sends one ICMP error message back to indicate that this packet cannot be sent
because TTL timeouts. Then, the first gateway re-sends the packet after the TTL domain
adds 1. Likewise, the second gateway returns a TTL timeout error and the process lasts until
the packet reaches the destination address. Once you record every source address for
loopback ICMP TTL timeout information, you have recorded the entire path passed by the IP
packet from the source address to the destination address.
The Traceroute command can run in user EXEC mode and privileged EXEC mode. The
command format is as follows:
The following are two examples that apply traceroute.In one example, network connectivity
is good. In another example, some gateways in a network are not connected.
1. Traceroute example where network connectivity is good:
DGS-3610# traceroute 61.154.22.36
< press Ctrl+C to break >
Tracing the route to 61.154.22.36
1 192.168.12.1 0 msec 0 msec 0 msec
2 192.168.9.2 4 msec 4 msec 4 msec
3 192.168.9.1 8 msec 8 msec 4 msec
4 192.168.0.10 4 msec 28 msec 12 msec
5 202.101.143.130 4 msec 16 msec 8 msec
6 202.101.143.154 12 msec 8 msec 24 msec
7 61.154.22.36 12 msec 8 msec 22 msec
From the above result, we can know clearly the following information: To access the host
with an IP address of 61.154.22.36, the network packet passes gateways 1 to 6 from the
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