Get started with BGP

First of all, my congratulations on taking the first step to start using BGP. The three most important concepts that you should also know about BGP are:

  • ASN (Autonomous System in Spanish), which is the unique identifier of each independent entity on the Internet, and are granted by the RIRs (in our region it is LACNIC)
  • IP prefix, which is a block / set of IP addresses, either IPv4 or IPv6 that will be originated by an ASN. These IP prefixes are also granted by the RIRs (in our region it is LACNIC)
  • Filters, which protects your network from potential errors from other ASNs, and protects other ASNs from your potential errors.

For pedagogical purposes I am going to simplify the technical part of the protocol, anyway I leave a link below to a formal definition and more in-depth information. I also emphasize that although I mention that the three most important concepts are ASN, IP Prefix and Filters; There are undoubtedly another series of very important concepts, but to begin with.

The good thing is that you can probably continue using your usual router, since this protocol is supported by the vast majority of routers for business or carrier use, it is also supported by several layer 3 switches.

By using BGP, and specifically eBGP (which is how BGP is called to networks outside your ASN), your network becomes an autonomous entity on the Internet, so a unique identifier is needed, which is the ASN that is “The identifying number of your organization on the Internet”.

The IP prefixes are the identifying numbers that you have to exchange packets on the Internet, in this case on the Internet only valid prefixes should be announced, which among other things exclude prefixes from private ranges and bogons. Regarding IP Prefixes, the minimum size accepted by most ASNs is / 24 for IPv4 prefixes and / 48 for IPv6 prefixes (although there are some ASNs that only accept / 32 as a minimum in IPv6), so you cannot by For example, originate a / 29 or / 28 prefix with your ASN, but it will have to be at least / 24 for IPv4. If you don’t know how to obtain your ASN and IP Prefixes in LACNIC, I recommend that you visit this guide.

Filters both input (IN) and output (OUT). The IN filters will determine all the routes that you will receive from the Internet and to which you will be able to send data, and which will therefore influence your upload traffic.

In the event that you want to receive the DFZ from your IP transit provider, you may have to check the maximum number of routes supported by your router or Layer 3 switch.

Technical Definition: BGP is the acronym for Border Gateway Protocol (or border gateway protocol in Spanish), which is a protocol through which routing information is exchanged between autonomous systems. For more information on the formal definition visit this article on Wikipedia.