There are two hops from the source device to the destination device. Use the tracert command to detect the path. When the first hop is detected, the source device sends a UDP packet with a TTL of 1 to a larger port of the destination device. When the packet reaches the middle hop, the TTL will change to 0, so the device responds to the source device. Respond to an ICMP______ message.

When configuring ISDN DCC, the customer made the following configuration on his MSR router:
[MSR] dialer-rule 1 ip permit
[MSR] interface dialer 0
[MSR-Dialer0] dialer enable-circular
[MSR-Dialer0] ip address 100.1.1.1 255.255.255.0
[MSR-Dialer0] dialer-group 1
[MSR-Dialer0] dialer route ip 100.1.1.2 8810052
Which of the following statements about this configuration are correct? (multiple choice)

PPP has to go through a series of negotiation process before establishing the link, the correct negotiation sequence is ___. (Fill in the code of each step one by one, there can be no spaces in between, such as: ABC)

The XYZ company administrator is subnetting the office network. It is required to divide a class B network segment into several subnets of equal size for office users in various departments, but there is no limit to the size of the subnets. There can be ___ kinds of division methods. (Please fill in Arabic numerals)

The MAC address table on a layer 2 switch is shown in the figure.

When the switch receives a frame with a destination MAC address of 00-13-72-8E-4E-C4 from the E1/0/2 interface, the switch will ______ the frame. (Multiple choice)