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the network 140.252.13. This could be done by either a static route in each host's routing
table, or by running a routing daemon in each host. A simpler way (and the method actually
used) is to utilize ICMP redirects.
Let's run the ping program from the host solaris on the top network to the host bsdi
(184.108.40.206) on the bottom network. Since the subnet IDs are different, proxy ARP can't
be used. Assuming a static route has not been installed, the first packet sent will use the
default route to the router gateway. Here is the routing table before we run ping:
solaris % netstat -rn
Destination Gateway Flags Ref Use Interface file:///D|/Documents%20and%20Settings/bigini/Docu.../homenet2run/tcpip/tcp-ip-illustrated/ip_rout.htm (11 of 17) [12/09/2001 14.46.51] Chapter 9. IP Routing 127.0.0.1
le0 (The entry for 220.127.116.11 is for IP multicasting. We describe it in Chapter 12.) If we specify
the -v option to ping, we'll see any ICMP messages received by the host. We need to
specify this to see the redirect message that's sent.
solaris % ping -sv bsdi
PING bsdi: 56 data bytes
ICMP Host redirect from gateway gateway (18.104.22.168)
to netb (22.214.171.124) for bsdi (126.96.36.199)
64 bytes from bsdi (188.8.131.52): icmp_seq=0. time=383. Ms
64 bytes from bsdi (184.108.40.206): icmp_seq=l. time=364. Ms
64 bytes from bsdi (220.127.116.11): icmp_seq=2. time=353. Ms
^? type interrupt key to stop
--bsdi PING Statistics-4 packets transmitted, 3 packets received, 25% packet loss
round-trip (ms) min/avg/max = 353/366/383
Before we receive the first ping response, the host receives an ICMP redirect from the
default router gateway. If we then look at the routing table, we'll see that the new route to
the host bsdi has been inserted. (This new entry is shown in a bolder font.)
Solaris % netstat -rn
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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