Tag: EGP

BGP Path Attributes: The BGP Path Selection Process

BGP Path Attributes

BGP has many attributes in choosing the best path. It is like an ice cream. It has many flavors. I bought Gianduia flavor from Gelato Messina while I was preparing this topic. I think I need loads of sugar to feed my brain as this BGP topic is robust and every attribute can be well-explained if we are going to lab it.

BGP’s attributes are mainly for path manipulation and these can influence either outbound or inbound traffic. It has a systematic process that it uses to choose the best path in the network.

BGP Path Selection Algorithm

The first thing that BGP checks is whether the WEIGHT is configured or not. WEIGHT is Cisco Proprietary so it is obvious that it prioritizes Cisco devices which has BGP WEIGHT configured. In short, if you are using Cisco devices, WEIGHT is the first thing it checks before it goes on with the series of standard BGP attributes. Keep in mind that WEIGHT is local to the router and doesn’t pass to other routers. The higher the value is more preferred. (more…)

The Internet Protocol: Border Gateway Protocol (BGP) Overview

Border Gateway Protocol (BGP) is an exterior gateway protocol used on the internet and ISPs to exchange routing and reachability information. BGP is a layer 4 path vector routing protocol that uses port 179. It is the only EGP that is still in use today. The current BGP version is BGPv4 which was published as RFC 4271 in 2006.

Unlike other IGPs (OSPF, EIGRP, or RIP), BGP has many metrics or attributes in choosing the best path in the network. These attributes are for path manipulation. We will check it one by one as those attributes influence either inbound or outbound traffic.

Difference Between Interior Gateway Protocol (IGP) and Exterior Gateway Protocol (EGP)?

When I first heard about Interior Gateway Protocol (IGP) and Exterior Gateway Protocol (EGP), I was just like, “what on bits and bytes are these?” If you are new to networks and you suddenly heard these on your first day, you might ignore the meaning and also the importance. However, you don’t have to memorize the meaning because you will know it by heart as days go by. (more…)