Download Cisco Packet Tracer from the course $($use a Windows $7$ VM if you cannot make it run on Windows $10),$ load the file example$1.$pkt and reply to the questions below:

NOTE: The IP addresses for the PCs are $192\mathrm{.}168\mathrm{.}100.$X$,$ where X is the PC #$,$ so$,$ for instance, the IP address of PC$12$ would be $192\mathrm{.}168\mathrm{.}100\mathrm{.}12.$ All PCs have a network mask $255\mathrm{.}255\mathrm{.}255\mathrm{.}128,$ i$.$e$.,$ their IP address is $192\mathrm{.}168\mathrm{.}100.$X$/25$ in CIDR notation.

Click on PC$10,$ then on the Desktop tab and finally on Command Prompt. Why PC$10$ cannot ping PC$129?$