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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 22.214.171.124) 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 Comment sun 126.96.36.199
1 on subnet 1
on author's Ethernet svr4 188.8.131.52 255.255.255.224 184.108.40.206 2 bsdi 220.127.116.11
2 on Ethernet
point-to-point slip 18.104.22.168 255.255.255.224 22.214.171.124 1 point-to-point 126.96.36.199 255.255.255.224 188.8.131.52 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.
- Spring '12