10 Ebgp Peerings for Ipv4

BGP Neighbor Types and eBGP Validation

By Default: eBGP peers must be directly connected, meaning they should share an immediate network connection.
AS Number Requirement: For eBGP peering, different Autonomous System (AS) numbers are required.
Configuration: Directly connected eBGP neighbors are configured using the "neighbor" command in BGP.

BGP Code Requirement: BGP code checks for directly connected peers by default, but there are scenarios where non-directly connected neighbors are needed.
Peering Options: Non-directly connected neighbors can include peering via loopback interfaces, through other routers or ASes.
Required Commands: To establish BGP sessions with non-directly connected neighbors, one of the following commands is required:
- ebgp-multihop: Specifies the number of hops away the neighbor is.
- disable-connected-check (Cisco Best Practice): Disables the connected check to allow peering with non-directly connected neighbors.

Definition: IPv4 Link-Local Addressing is defined in RFC 3927 & 6890.
Not Routable on the Internet: Addresses within the 169.254.0.0/16 address block are not publicly routable on the global Internet. They are reserved for local network communication.

Validation Commands: eBGP validation can be accomplished using the following commands for verification:
- show ip bgp summary: Provides a summary of BGP information for IPv4.
- show bgp ipv4 unicast summary: Displays a summary of BGP information for IPv4 unicast routes.
- show ip bgp neighbor [neighbor IP]: Shows detailed information about a specific BGP neighbor in IPv4.
- show bgp ipv4 unicast neighbor [neighbor IP]: Provides detailed information about a specific BGP neighbor for IPv4 unicast routes.

Understanding different BGP neighbor types and using validation commands is essential for proper BGP configuration and maintenance.