Two routers are connected through the serial port, but the interconnect interface cannot be pinged.
Now check the port status as follows:

From the above information can determine what is the reason?

Which of the following features does the IS-IS protocol have? (Multiple choice)

According to the configuration shown in the figure below, you can know that R4 has ____ interfaces that are advertised into IS-IS?

In multicast network, what happens to multicast traffic that cannot be forwarded normally? (Multiple choice)

The attacker responds to the request by sending ICMP and sets the destination address of the request packet to the broadcast address of the victim network to achieve the purpose of the attack.
So what kind of attack does this behavior belong to?