What is BGP commands?

BGP commands are specific instructions used to configure and manage the Border Gateway Protocol (BGP) on network devices, such as routers. These commands allow network administrators to establish peering relationships with other BGP speakers, announce network prefixes, control routing policy, and monitor the BGP process.

Understanding the Role of BGP Commands

BGP is the primary routing protocol used on the internet to exchange routing information between autonomous systems (AS). Configuring BGP involves telling a router which other BGP routers (neighbors) it should exchange routing information with and which network prefixes it should advertise to the BGP cloud. BGP commands are the tools used to perform these configurations.

Essential BGP Configuration Commands

Based on common BGP configurations, including information provided in resources like BGP configuration tutorials, some key commands are fundamental for getting BGP operational.

Establishing BGP Peering: The neighbor Command

One of the first steps in configuring BGP is establishing a connection, or peering, with another BGP speaker. This is done using the neighbor command.

• Purpose: To initiate a BGP session with a specified remote BGP peer.
• Syntax (Conceptual): neighbor <remote-ip-address> remote-as <remote-as-number>
• Key Requirements: As highlighted in BGP configuration guides, for peering to be successful, you must ensure:
  • The specified remote-ip-address of the neighbor matches the interface IP address on the neighbor's device used for the BGP connection.
  • The remote-as-number is correctly configured to match the autonomous system number of the BGP neighbor.
• Process: Issuing the neighbor command tells your router to attempt to establish a TCP connection (on port 179) with the specified neighbor's IP address for the purpose of exchanging BGP messages.

Advertising Networks: The network Command

Once peering is established, your router needs to inform its neighbors about the network prefixes that it can reach or originates. This is typically done using the network command.

• Purpose: To inject a specific network prefix into the BBGP routing table for advertisement to neighbors.
• Syntax (Conceptual): network <network-address> [mask <subnet-mask>]
• Usage Example: To advertise the network address associated with an interface, such as a loopback interface (often used for stability in BGP peering or as a source for advertised prefixes), the network command is used with the specific network and mask. For example, network 192.168.1.0 mask 255.255.255.0.

These two commands, neighbor and network, represent foundational elements in configuring BGP for basic operation – establishing communication with peers and announcing routes.

Summary of Key BGP Commands

Command	Primary Purpose	Key Configuration Detail
neighbor	Establish BGP peering sessions with remote BGP speakers	Requires correct remote IP address and remote AS number.
network	Advertise network prefixes into the BGP routing table	Specifies the network address and subnet mask to advertise.

While neighbor and network are crucial starting points, BGP configurations often involve many other commands to control routing policies, filter routes, influence path selection, and manage BGP attributes, demonstrating the protocol's complexity and power.