TCP IP Illustrated

252111 traceroute to 140252111 140252111 30 hops max

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Unformatted text preview: emini is multihomed, with two Ethernet interfaces. First let's verify that we can Telnet to both addresses: sun % telnet 140.252.1.11 daytime Trying 140.252.1.11 ... Connected to 140.252.1.11. Escape character is '^]'. Sat Mar 27 09:37:24 1993 Connection closed by foreign host. sun % telnet 140.252.3.54 daytime Trying 140.252.3.54 ... Connected to 140.252.3.54. Escape character is '^]'. Sat Mar 27 09:37:35 1993 Connection closed by foreign host. So there is no connectivity difference between the two addresses. Now we'll use traceroute to see if there is a different route for each address: sun % traceroute 140.252.1.11 traceroute to 140.252.1.11 (140.252.1.11), 30 hops max, 40 byte packets 1 netb (140.252.1.183) 299 ms 234 ms 233 ms 2 gemini (140.252.1.11) 233 ms 228 ms 234 ms sun % traceroute 140.252.3.54 traceroute to 140.252.3.54 (140.252.3.54), 30 hops max, 40 byte packets 1 netb (140.252.1.183) 245 ms 212 ms 234 ms 2 swnrt (140.252.1.6) 233 ms 229 ms 234 ms 3 gemini (140.252.3.54) 234 ms 233 ms 234 ms There is an extra hop if we use the address on subnet 140.252.3. Let's find the reason for the extra hop. (The router swnrt is R3 from Figure 3.6.) file:///D|/Documents%20and%20Settings/bigini/Doc...omenet2run/tcpip/tcp-ip-illustrated/snmp_sim.htm (27 of 33) [12/09/2001 14.47.40] Chapter 25. SNMP: Simple Network Management Protocol Figure 25.29 shows the arrangement of the systems. We can tell from the traceroute output that the host gemini and the router swnrt are both connected to two networks: 140.252.1 and 140.252.3. Figure 25.29 Topology of systems being used for example. Recall in Figure 4.6 that we explained how proxy ARP is used by the router netb to make it appear as though sun was directly connected to the Ethernet 140.252.1. We've also omitted the modems on the SLIP link between sun and netb, since they're not relevant to this discussion. In Figure 25.29 we show the path of the Telnet data using dashed arrows, when the address 140.252.3.54 is specified. How do we know that the return packets go dire...
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