RACOM M!DGE3, Руководство пользователя

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Selects the way how the routing rule source protocol is compared.
Protocol
List box {System; BGP; BGP external; BGP internal}, default = "System"
Selection of the protocol origin. “System” – stands for rules from the ordinary routing table.
Filter BGP path
List box {Off; Is empty; Not empty}, default = "Off"
Compares BGP routing rule path if it is empty (i.e. the rule originates in this AS).
Action
List box {Accept; Reject; Pass}, default = "Accept"
Defines what action is taken on the routing rule. "Pass" continues in processing.
7.2.4. BGP
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange
routing and reachability information among autonomous systems. BGP is classified as a path-vector
routing protocol, and it makes routing decisions based on paths, network policies, or rule-sets configured
by a network administrator.
7.2.4.1. Description
BGP splits the network into Autonomous Systems (AS) which are identified by a specific number. Indi-
vidual BGP routers are interconnected with their neighbors using TCP connections. Any connection
can travel over multiple hops. Any connection can be secured using MD5 signatures.
Connections inside the AS are called ‘internal’ (iBGP):
• All BGP routers within given AS must be fully interconnected – every router must have connection
to all other routers.
• It is possible to define ‘Route reflectors’ – they must be fully interconnected. The other routers behave
as Route reflector clients and they need a connection to their reflector only. Route reflector and its
clients form a ‘cluster’. It is possible to create a cluster with multiple Route reflectors for the purpose
of backup.
• The iBGP router having a higher local preference will be preferred during the internal AS path selection.
Connections to another AS are called ‘external’ (eBGP):
• It is possible to communicate from the router to the neighbor AS the MED (Multi-Exit Discriminator)
metric designating which of the AS border routers will be used as an input point.
When the routing rules are spread across the multiple AS, those AS are added into the accumulated
path (BGP path). Path length is the primary criteria during the decision which of the routing rules will
be used.
It is possible to prescribe routing rules toward this router which will be spread across the network
(Static rules).
It is possible to control the routing rules which are imported into the M!DGE3 unit from the BGP protocol
and those that are exported into the BGP protocol from the unit by using ‘filters’.
M!DGE3 Cellular Router – © RACOM s.r.o. 92
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