Table of Contents
Question
What are three well-known mandatory BGP attributes? (Choose three.)
A. MED
B. origin
C. community
D. AS path
E. next hop
Answer
B. origin
D. AS path
E. next hop
Explanation
B. origin
D. AS path
E. next hop
The three well-known mandatory BGP attributes are:
- Origin: The origin attribute is used to identify the source of the route information. It can have three possible values: IGP (Interior Gateway Protocol), EGP (Exterior Gateway Protocol), or Incomplete. IGP indicates that the route was originated within the local AS, EGP indicates that the route was learned from another AS, and Incomplete indicates that the source of the route is unknown or not specified.
- AS path: The AS path is a sequence of AS numbers that represents the path taken by a route to reach the destination network. When a route is advertised from one AS to another, the advertising AS adds its AS number to the AS path. This attribute is used by BGP to prevent routing loops and to select the best path to a destination based on AS path length.
- Next hop: The next hop attribute specifies the IP address of the next-hop router that should be used to reach the destination network. When a route is advertised between BGP peers, the next hop address is set to the IP address of the advertising router. This attribute is crucial for forwarding packets along the correct path towards the destination network.
The other two options, A. MED and C. community, are not well-known mandatory BGP attributes.
- A. MED: This is an optional attribute that stands for Multi-Exit Discriminator. It is used to influence the inbound traffic from multiple entry points into an AS by indicating a preference for one entry point over another.
- C. Community: This is an optional attribute that allows a group of destinations to share some common property or policy. It is used to simplify the configuration and administration of routing policies by applying them to a set of routes with a common community value.
In summary, the three well-known mandatory BGP attributes are origin, AS path, and next hop. These attributes provide crucial information about the route’s source, the ASes it has traversed, and the next-hop router’s IP address.
Reference
- JNCIS-SP Certification | Juniper Networks US
- Ultimate Guide: BGP Attributes and Path Selection (comparitech.com)
- The BGP Attributes (catchpoint.com)
- BGP Attributes – Path Selection algorithm -BGP Attributes influence inbound and outbound traffic policy. (techmusa.com)
- BGP Path Selection > CCNP Routing and Switching Quick Reference: BGP and Internet Connectivity | Cisco Press
- BGP Well Known Mandatory Attributes | How the BGP works | N-Study
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