The Next Header field information only exists in the IPv6 message and is used to indicate whether there is an extended header in IPv6.

Which of the following description about the OSPF virtual link is true?

Which of the following description about interfaces on the switch Access procedure receives data frame mode is correct?

Because BGP is the EGP routing protocol, BGP routing policies can only be deployed between EBGP neighbors, and routing policies deployed between IBGP neighbors are invalid.

The IS-ISL eve 1-1 neighbors of R3 and R4 are not established. According to the information in this figure, what are the possible reasons?
[R3] display isis error Hello packet errors: ... ... Repeated System ID: 0 Bad Circuit Type 0 Bad TLV Length: 0 Zero Holding Time 0 Unusable IP Addr: 0 Repeated IPv4Addr 0 Mismatched Area Addr ( L 1 ) :13 Mismatched Proto 0 SNPA Conflicted(L AN): 0 Mismatched Level 0 Mismatched Max Area Addr: 0 Bad Authentication 0 ... ... [R3]