What is BGP

• BGP stands for Border gateway protocol, this is an EGP (Exterior Gateway Protocol) used to route and reach information on autonomous systems on the internet
• This protocol is classified as a Path vector protocol, meaning that the routing decisions are based on paths, network policies, or rules created by the network admin
• An autonomous system is a collection of connected internet protocol routing prefixes, these are under the control of a single admin and they have clearly defined routing policies to the internet
• ASN () is allocated for each AS that uses BGP, this is a unique identifier assigned for the network so it can be identified on the internet.

BGP Operations

• BGP has manually configured peers that create a TCP session on port 179, BGP sends keep-alive messages every 60 seconds to maintain a connection with its peers.
• BGP is unique in the fact that it uses TCP as its transport protocol

Setting up BGP

• From the internal router, you will want to set the default route to the ip address of the ISP using the command: default route IP address Subnetmask
• Use the command default-information originate in ospf config to send a default route to the other routers in the area
• use redistribute ospf 1 in BGP config to advertise co routes to the entire area

Deine Router instance

• router bgp AS_NUMBER_FOR_ROUTER

Identify peers

• In config-router: neighbor (IP of peer) remote-as (as number of peer)

Advertising within the AS

• In config-router: network (IP Address) mask (Subnet)