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1 bsdi (18.104.22.168) 110 ms 110 ms 110 ms
2 svr4 (22.214.171.124) 110 ms 120 ms 110 ms
This time the IP address printed for host bsdi is 126.96.36.199, the SLIP interface, while
previously it was 188.8.131.52, the Ethernet interface. Since traceroute also tries to
print the name associated with an IP address, the names can change. (In our example both
interfaces on bsdi have the same name.)
Consider Figure 8.3. It shows two local area networks with a router connected to each LAN.
The two routers are connected with a point-to-point link. If we run traceroute from a
host on the left LAN to a host on the right LAN, the IP addresses found for the routers will
be if1 and if3. But going the other way will print the IP addresses if4 and if2. The two
interfaces if2 and if3 share the same network ID, while the other two interfaces have
different network IDs. Figure 8.3 Identification of interfaces printed by traceroute.
Finally, across wide area networks the traceroute output is much easier to comprehend
if the IP addresses are printed as readable domain names, instead of as IP addresses. But
since the only piece of information traceroute has when it receives the ICMP message
is an IP address, it does a "reverse name lookup" to find the name, given the IP address. file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/tracerou.htm (6 of 17) [12/09/2001 14.46.47] Traceroute Program This requires the administrator responsible for that router or host to configure their reverse
name lookup function correctly (which isn't always the case). We describe how an IP
address is converted to a name using the DNS in Section 14.5. 8.4 WAN Output
The output shown earlier for our small internet is adequate for examining the protocols in
action, but more a realistic use of traceroute involves larger internets such as the worldwide
Internet. Figure 8.4 is from the host sun to the Network Information Center, the NIC.
sun % traceroute nic.ddn.mil
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12