Ch 14 - Advanced BGP Concepts

Question 1

LOCAL_PREF

Answer 1

A BGP path attribute that is communicated throughout a single AS to signify which route of multiple possible routes is the best route to be taken when leaving that
AS. A larger value is considered to be better.

Question 2

AS_PATH prepending

Answer 2

This term has two BGP-related definitions. First, it is the normal process in which a router, before sending an Update to an eBGP peer, adds its local ASN to
the beginning of the AS_PATH path attribute. Second, it is the routing policy of purposefully adding one or more ASNs to the beginning of a route’s AS_PATH path attribute, typically to lengthen the AS_PATH and make the route less desirable in the BGP decision process.

Question 3

best path algorithm

Answer 3

A set of rules by which BGP examines the details of multiple BGP routes for the same NLRI and chooses the single best BGP route to install in the local BGP
table.

Question 4

Routing Table Manager

Answer 4

A component of IOS that manages the process of adding IP routes to the IP routing table. RTM considers routes from all routing sources (static, connected,
routing protocols) and chooses the best route to add for a given prefix/length.

Question 5

RIB failure

Answer 5

An event that occurs when the Routing Table Manager (RTM) attempts to add a route to the IP routing table, but a problem exists with the route that prevents RTM from adding the route.

Question 6

path attribute

Answer 6

Generally describes characteristics about BGP paths advertised in BGP Updates.

Question 7

BGP synchronization

Answer 7

In BGP, a feature in which BGP routes cannot be considered to be a best route to reach an NLRI unless that same prefix exists in the router’s IP routing table as learned via some IGP.

Question 8

iBGP Mesh

Answer 8

A BGP design convention in which all BGP peers internal to a single AS have been directly peered so that all pairs of internal BGP routers are neighbors.

Question 9

next-hop self

Answer 9

A BGP configuration setting that tells the local router to change the NEXT_HOP path attribute to refer to its own BGP Update Source when advertising routes to BGP
neighbors.

Question 10

BGP soft reset

Answer 10

The process of restarting a BGP neighbor relationship without closing the underlying TCP connection, instead resending full Updates to the neighbor and asking for
the neighbor to send a full Update again.

Question 11

BGP hard reset

Answer 11

The process of restarting a BGP neighbor relationship by closing the TCP connection, causing both neighboring routers to remove all paths formerly learned from that neighbor from their respective BGP tables.

Question 12

BGP Weight

Answer 12

A local Cisco-proprietary BGP setting that is not advertised to any peers. A larger value is considered to be better.