Answer» - internal Border Gateway Protocol(iBGP): Inside autonomous systems, IBGP is used. Its purpose is to feed data to your internal routers. For PREFIX learning, all devices in the same autonomous system must form a full MESH topology or use either Route reflectors or Confederation.
- external Border Gateway Protocol (EBGP): It is employed between autonomous systems. It's used and deployed at the edge or border router, which connects two or more autonomous systems together. It is the protocol that allows networks from various organisations or the Internet to COMMUNICATE with one another.
The following table lists the differences between the internal Border Gateway Protocol and the external Border Gateway Protocol: | internal Border Gateway Protocol (iBGP) | external Border Gateway Protocol (eBGP) |
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| It connects two BGP routers in a single autonomous system. | It connects two BGP routers in separate independent systems. | | Its Administrative Distance is set to 200 by default. | Its Administrative Distance is set to 20 by default. | | IBGP routes obtained from an IBGP peer can be broadcast to an EBGP peer but not to another IBGP peer. | EBGP routes can be published to EBGP and IBGP peers when received from an EBGP peer. | | It necessitates the use of full mesh topology. | It does not necessitate a complete mesh topology. | | Within the same corporation, it's used. | It's used between corporations or between corporations and Internet service providers. | | For loop prevention, it employs BGP SPLIT Horizon. | It prevents loops by using an AS path. | | TTL (Time To Live) = 255 is the default setting for peers. | TTL (Time To Live) = 1 is the default setting for peers. | | Attributes such as local preference are exchanged between IBGP peers. | Attributes such as local preference are not communicated between EBGP peers. | | The next hop remains constant when a route is advertised to an IBGP peer. | When a route is announced to an EBGP peer, the local router becomes the next hop. |
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