This is part of a question from a networking class.
A router has IP 18.104.22.168 on the local network 22.214.171.124/21(through eth0), and uses IP address 126.96.36.199 to communicate with the internet through eth1.
And the question asks for how many addresses are available for hosts in this local network.
I know there are 32 bits in the address, where 21 bits are used to identify the network, leaving 32-21 = 11 bits available, which give 2^11 addresses.
Within this 2^11 addresses, all-one address and all-zero address are not allowed to be used. And the router uses 188.8.131.52 and 184.108.40.206.
I have a few questions about this setup:
Since the router has an external address of 220.127.116.11, does that mean the ISP's gateway also takes an address in the 18.104.22.168/21 range?
How do this router and the ISP's gateway setup their routing tables to allow this configuration?
Usually I only see that a router connects 2 different networks, and this one looks strange.