Tuesday, March 10, 2009


Autonomous system is a set of routers under a single technical administration , using an igp and common metrics to route packets withing AS

* usage of bgp

# bgp is more appropriate if one of the following conditions exits

- a.s working as transit a.s (isp)
- a.s connected to multiple a.s
- data traffic path entering or leaving a.s need to be manipulated

#when do you donot prefer bgp:

- if it is a single-home a.s
- lack of resources like memory and less processing power in routers
- low bandwidth link between a.s
- limited understanding of bgp route filtering and path selection process

#Bgp features

-open standard protocol
-advance distance vector protocol
- path vector protocol
-supports flsm, vlsm , cidr , auto and manual summary (bgp version 4)
-it is an egp
-designed to scale huge internetwork like internet
-updates are incemental and triggered
-it send updates to manually defined neighbor as unicast
-bgp is an application layer protocol , uses tcp port 179 for reliability
-metric = attributes
- administrative distance
- 20 external updates
-200 internal updates
-bgp is not designed for load balancing . uses only one path per network

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