What is BGP

Flashcards on BGP based on lecture notes. Vocabulary style flashcards with terms and definitions.

Border Gateway Protocol (BGP)

A standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet.

Path-Vector Routing Protocol

A path-vector routing protocol, and it makes routing decisions based on paths, network policies, or rule-sets configured by a network administrator.

Interior Border Gateway Protocol (IBGP)

BGP used for routing within an autonomous system

Exterior Border Gateway Protocol (EBGP)

The Internet application of the protocol

BGP4

The current version of BGP

Multiprotocol Extensions which is Multiprotocol BGP (MP-BGP)

Allows BGP4 to carry a wide range of IPv4 and IPv6 address families.

BGP Neighbors/Peers

Established by manual configuration among routers to create a TCP session on port 179

Border or Edge Routers/eBGP peers

Routers on the boundary of one AS exchanging information with another AS

Autonomous System Number (ASN)

A special number assigned by IANA used primarily with Border Gateway Protocol which uniquely identifies a network under a single technical administration that has a unique routing policy, or is multi-homed to the public internet.

PUBLIC ASN

An ASN in the public range is globally unique and may be announced on the global Internet to your ISP or at an internet exchange point (peering point) via BGP.

PRIVATE ASN

The private ASN should not be seen on the global Internet (they shouldn't be announced via your exterior gateway routing protocol).

Internal Border Gateway Protocol (iBGP)

A routing protocol used on the internet for exchanging routing information between two or more routers within an autonomous system (AS)--hence the use of the word 'Internal.'

External Border Gateway Protocol (eBGP)

A routing protocol used to exchange information between two autonomous systems (AS).

BGP update-source command

Tells BGP which interface to source the BGP packets out of.

Split horizon

A method used by distance vector protocols to prevent network routing loops: Never send routing information back in the direction from which it was received

iBGP split horizon rule

A BGP router will not advertise prefixes from one iBGP neighbor to another iBGP neighbor.

BGP Route Reflector

BGP route reflectors reflect learnt routes to their adjacent neighbors.

Route Reflector Clusters

A route reflector and its clients, or possibly multiple route reflectors sharing the same clients.

Confederation

An AS that has been subdivided into a group of sub-autonomous systems, known as member autonomous systems.

ASCONFEDSEQUENCE

AS numbers along a path to a destination. It is used in exactly the same way as the AS_SEQUENCE, except that the AS numbers in the list belong to autonomous systems within the local confederation.

ASCONFEDSET

Unordered list of AS numbers along a path to a destination. It is used in exactly the same way as the AS_SET, except that the AS numbers in the list belong to autonomous systems within the local confederation.

Route Recursion

The simple process that all routers complete so they can ultimately find out what interface to use when routing to a particular prefix (Fancy term for route).

Next-Hop-Self Command

We force BGP to use a specific next hop instead of protocol’s choice.

BGP weight attribute

First on the list in the BGP best path algorithm, local to the router on which it is configured, and not passed between neighbors.

BGP Local Preference

Second BGP attribute, used to choose the exit path for an autonomous system. Attribute has to be set inbound on routes being received to influence the outbound routing behaviour

AS Path Prepend

The shortest path that has the lowest number of transiting AS is the preferred.

BGP Origin Codes

Defines the Origin of routing information, aka, how a route became a BGP route.

MED (Multi-Exit Discriminator)

Optional BGP attribute that’s used when there are multiple external points for a single AS.

bgp always-compare-med command

Command ensures the comparison of the MED for paths from neighbors in different autonomous systems.

EIGRP leak map

Allows you to advertise a specific prefix within the range of a summary advertisement, as well as the summary itself.

Prefix list

Like access lists for route advertisements (prefixes)

Atomic Aggregate

Purpose of the attribute is to alert BGP speakers along the path that some information have been lost due to the route aggregation process and that the aggregate path might not be the best path to the destination.

BGP Aggregation

BGP can aggregate addresses when configured manually but will also advertise the original longer prefix advertisements along with the summarised version.

No-advertise BGP community attribute

Command tells the receiver not to pass it on to its neighbours (advertise tags to other networks).

local AS

Function is used with BGP confederations where a defined private AS can be within another AS. When used without confederations it would be like no-export.

BGP Conditional Route Injection

The BGP Conditional Route Injection feature allows you to originate a prefix into a BGP routing table without the corresponding match.

BGP Maximum-Prefix feature

The BGP Maximum-Prefix feature allows you to control how many prefixes can be received from a neighbor.