TCP IP Illustrated

A simpler way and the method actually used is to

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: or 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 (140.252.13.35) 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 Routing Table: 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 127.0.0.1 140.252.1.0 224.0.0.0 default 127.0.0.1 140.252.1.32 140.252.1.32 140.252.1.4 UH U U UG 0 3 3 0 848 15042 0 5747 lo0 le0 le0 (The entry for 224.0.0.0 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 (140.252.1.4) to netb (140.252.1.183) for bsdi (140.252.13.35) 64 bytes from bsdi (140.252.13.35): icmp_seq=0. time=383. Ms 64 bytes from bsdi (140.252.13.35): icmp_seq=l. time=364. Ms 64 bytes from bsdi (140.252.13.35): 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 Routing Table: Destination 127.0.0.1 140.252.13.35 140.252.1.0 224.0.0.0 default Gateway 127.0.0.1 140.252.1.183 140.252.1.32 140.252.1.32 140.252.1.4 Flags UH HGHD U U UG Ref 0 0 3 3 0 Use 848 2 15045 0 5747...
View Full Document

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.

Ask a homework question - tutors are online