TCP IP Illustrated

The new router requirements rfc almquist 1993

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Unformatted text preview: ation network ID. We'll see in Chapter 10 that RIP does not support variable-length subnets, while RIP Version 2 and OSPF do. We don't have a problem with our example, since RIP isn't required on the author's subnet. Figure 3.11 shows the IP address structure used within the author's subnet. The first 8 bits of the 11bit subnet ID are always 13 within the author's subnet. For the remaining 3 bits of the subnet ID, we use binary 001 for the Ethernet, and binary 010 for Figure 3.11 Using variable-length subnets. file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/ip_inter.htm (14 of 19) [12/09/2001 14.46.37] Chapter 3. IP: Internet Protocol the point-to-point SLIP link. This variable-length subnet mask does not cause a problem for other hosts and routers in the 140.252 network-as long as all datagrams destined for the subnet 140.252.13 are sent to the router sun (IP address 140.252.1.29) in Figure 3.10, and if sun knows about the 11-bit subnet ID for the hosts on its subnet 13, everything is fine. The subnet mask for all the interfaces on the 140.252.13 subnet is 255.255.255.224, or 0xffffffe0. This indicates that the rightmost 5 bits are for the host ID, and the 27 bits to the left are the network ID and subnet ID. Figure 3.12 shows the allocation of IP addresses and subnet masks for the interfaces shown in Figure 3.10. Host IP address Subnet mask Net ID/Subnet ID Host ID Comment sun 140.252.1.29 140.252.13.33 255.255.255.0 255.255.255.224 140.252.1 140.252.13.32 29 1 on subnet 1 on author's Ethernet svr4 140.252.13.34 255.255.255.224 140.252.13.32 2 bsdi 140.252.13.35 140.252.13.66 255.255.255.224 255.255.255.224 140.252.13.32 140.252.13.64 3 2 on Ethernet point-to-point slip 140.252.13.65 255.255.255.224 140.252.13.64 1 point-to-point 140.252.13.63 255.255.255.224 140.252.13.32 31 broadcast addr on Ethernet Figure 3.12 IP addresses on author's subnet. The first column is labeled "Host," but both sun and bsdi also act as routers, since the...
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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.

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