172.16.10.32/24 represents

In the STP protocol, set all the switches are configured the same priority, the MAC address of switch 1 00-e0-fc-00-00-40, the MAC address of the switch 2 00-e0-fc-00-00 -10, the MAC address of the switch 3 00-e0-fc-00-00-20, the MAC address of the switch 4 is 00-e0fc-00-00-80, is the root switch should be

Refer to the graphic. The data is transmitted using IPsec tunnel mode. The fields of which headers will be authenticated?

To determine: the standard HDLC protocol suite of protocols are running on synchronous serial lines above.

The last option field (option) of an IPv4 packet is a length-variable and optional field. What is the maximum length of this field?