Subnet it yourself
Work out the numbers first, then build them. Answer the questions about the address 172.16.40.77/27. Then give router R1 two /27 subnets: Gi0/0 gets the first usable address of 172.16.40.64/27, and Gi0/1 the first usable address of the next /27 subnet. Address the PCs so they can talk across the router:
- PC1: the second usable address of the Gi0/0 subnet
- PC2: the second usable address of the Gi0/1 subnet
How it works: this is VulnTech NetLab, a network simulator running in your browser. Click a device in the diagram to open its console and type commands, just like on real equipment (? shows help, Tab finishes a word). Click a cable to inspect it. Tasks tick themselves off as you complete them; questions are answered in the box under each task. Your work is kept if you reload; Reset starts the network over.
Solution explanation
/27 means a mask of 255.255.255.224 and a block size of 32 in the last octet: subnets .0, .32, .64, .96 ... 77 is in the .64 block, so the network is .64 and the broadcast .95, with 30 usable hosts (.65 to .94). The next subnet is .96 to .127. With the router holding the first host of each subnet and the PCs using it as their gateway, traffic crosses between the two subnets.
Show solution
[R1]
enable
configure terminal
interface g0/0
ip address 172.16.40.65 255.255.255.224
no shutdown
interface g0/1
ip address 172.16.40.97 255.255.255.224
no shutdown
end
show ip route | begin Gateway
[PC1]
netsh interface ip set address "Ethernet" static 172.16.40.66 255.255.255.224 172.16.40.65
[PC2]
netsh interface ip set address "Ethernet" static 172.16.40.98 255.255.255.224 172.16.40.97
[PC1]
ping 172.16.40.98