IP Subnetting and Variable Length Subnet Masks (VLSMs)
Find the valid host
By looking at the router’s IP address on Ethernet0, what IP address, subnet mask, and valid host range could be assigned to the host?
The IP address of the router’s Ethernet0 is 192.168.10.33/27. As you already know, a /27 is a 224 mask with a block size of 32. The router’s interface is in the 32 subnet. The next subnet is 64, so that makes the broadcast address of the 32 subnet 63 and the valid host range 33–62.
Host IP address: 192.168.10.34–62 (any address in the range except for 33, which is assigned to the router).
Mask: 255.255.255.224 Default gateway: 192.168.10.33
Figure 3.15 shows two routers with Ethernet configurations already assigned. What are the host addresses and subnet masks of hosts A and B?
RouterA has an IP address of 192.168.10.65/26 and RouterB has an IP address of 192.168.10.33/ 28. What are the host configurations? RouterA Ethernet0 is in the 192.168.10.64 subnet and RouterB Ethernet0 is in the 192.168.10.32 network.
Host A IP address: 192.168.10.66–126 Host A mask: 255.255.255.192 Host A default gateway: 192.168.10.65 Host B IP address: 192.168.10.34–62 Host B mask: 255.255.255.240 Host B default gateway: 192.168.10.33
Just a couple more examples and then this chapter is history. Hang in there! Figure 3.16 shows two routers; you need to configure the S0/0 interface on RouterA. The network assigned to the serial link is 172.16.17.0/22. What IP address can be assigned?