What information does a path attribute contain?

• A. AS Path only
• B. Attribute type, length and value
• C. NLRI and next-hop
• D. Router ID and neighbor address

Answer: (B)

Path attributes in BGP are encoded as a type–length–value structure for each attribute carried in an update. The type identifies what the attribute is (for example NEXT_HOP, ORIGIN, or AS_PATH), the length indicates how many bytes the value uses, and the value contains the actual data for that attribute. This TLV-style format allows multiple attributes to be carried together, each with its own type, length, and value. The NLRI (the prefixes being announced) is sent separately after the attributes, and is not embedded within the path attribute data. Session details like router ID or neighbor address are not part of the path attribute data. So the information a path attribute contains is the type, length, and value.