Introduction of BGP

Introduction of BGP

The Border Gateway Protocol (BGP) announces, learns and selects the best routes within the Internet. When they connect to Internet service providers, they generally use BGP to exchange routing information. Internet service providers around the world share routing information with one or more ISPs.

Autonomous system

A system of autonomy is a set of networks under a management technique. IGPs such as OSPF EIGRP operate within an independent system. We use BGP between independent systems to exchange routing information without loops.

Internal and external BGP

BGP is defined in two neighbor categories.
The internal BGP (iBGP) works within the same system itself.
External BGP (E BGP) operates between the multiple autonomy system

BGP features

BGP is an open standard protocol.
An external gateway protocol designed to guide an inter-AS domain to extend the reach of a large network network such as the Internet
Its support without class, VLSM, CIDR, automatic summary and manual
Incremental updates The BGP engine sends updates to the selected environment manually as unicast.
BGP is an application layer protocol that uses TCP for reliability, TCP port 179
Metric is qualities
The administrative distance is 20 for external updates (EBGP) and 200 for internal updates (i BGP)
Types of ISP connections
Lonely Homed
Double home sites
Multiple legs
Dual Multi-Rocket


A single start site with an ISP connection is a single start. Staying alone is a good place for a site that does not rely heavily on the Internet or WAN. You can announce a fixed route or route and receive a default route from your ISP.

Double stored

The double-link site has two connections from the same ISP from one or two routers. One of the links may be basic and the other a backup, or the site may have a balanced load on both connections. We can use static or dynamic routing.


Multi-homing is a link to connect one or more ISPs at the same time. This is done for redundancy and backup if an Internet service provider fails and for better performance if an Internet service provider provides a better route for frequently used networks. Multi-homed U also offers an independent ISP solution. BGP is generally used with multi-homed connections.

Double home

Dual-multi-homed means having two connections with multiple ISPs. The multipoint duplex gives you maximum redundancy. BGP is used with ISP and can be implemented internally as well.
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