In order to publish the external routes introduced by the NSSA area to other areas, the Type 7 LSA needs to be converted into a Type 5 LSA so that it can be announced in the entire OSPF network. By default, the router that performs LSA conversion is the area border router (ABR) with the largest router ID in the NSSA area.

Which of the following is not included in the OSPF Hello message?

After basic QinQ is configured on an interface of a switch, the switch adds the default VLAN tag of the interface to packets only when the interface receives tagged packets. In this way, the VLAN space is expanded.

In order to protect the BGP protocol from attacks, Keychain authentication can be used between BGP neighbors to reduce the possibility of attacks. The keychain has a set of passwords that can be automatically switched according to the configuration, which is suitable for networks with high security requirements.

On the network shown in the figure, PC1 and PC2 are connected to the same switch (SW1) and belong to the same VLAN.

Which of the following are possible causes of a communication failure between PC1 and PC2?