In this post, we will compare BGP and EIGRP. We will look at some of the important aspects when we compare BGP vs EIGRP. Although EIGRP is used as an IGP and BGP is used mainly as an External routing protocol, we will compare from many different design aspects. Also, BGP can be used as an Internal IGP protocol as well and we will take that into consideration as well.
We prepared the above comparison chart for BGP vs EIGRP comparison. We will look at some of those important Comparison criteria from a design point of view.
BGP vs EIGRP Scalability
One of the biggest reasons we choose BGP, not EIGRP is Scalability. BGP is used as a Global Internet routing protocol and as of 2022, the Global routing table size for IPv4 unicast prefixes is around 900 000. So almost a million prefixes we carry over BGP on the Internet. So, proven scalability for BGP we can say. EIGRP usually can carry only a couple of thousands of prefixes, this is one of the reasons, EIGRPrp is used as an Internal dynamic routing protocol, not over the Internet.
BGP vs EIGRP in Full Mesh, Ring and Hub and Spoke Topologies
The full mesh may require a lot of logical connections, meaning BGP neighborship or EIGRP adjacencies. BGP Full Mesh is required because of the Split Horizon loop prevention requirement of BGP. But with the BGP Route Reflector, BGP can work well and can scale well in Full Mesh topologies. When it comes to large-scale Hub and Spoke topologies, EIGRP is a very suitable protocol for it. DMVPN is a very good example of this kind of topologies and both EIGRP and BGP are the most suitable protocols for the large Hub and Spoke topologies. Ring topologies are usually a nightmare for many aspects of every routing protocol. Converge slowly, hard for the capacity planning as well.
BGP vs EIGRP Fast Reroute
EIGRP can support IP Fast Reroute. BGP also with BGP PIC, Prefix Independent Convergence supports BGP Fast Reroute, so both protocols can give us data plane protection opportunity. Although Fast convergence in the control plane can be achieved with EIGRP Feasible Successor, because it can't provide a fast reroute, which is a data plane convergence mechanism, we won't further discuss it here.
BGP vs EIGRP Standard
When we compare EIGRP vs BGP from their standardization point of view, we need to know that BGP is a standard, and there is many standard track RFC for it, EIGRP RFC 7868 is only an informational track, thus EIGRP is not an IETF standard protocol.
BGP vs EIGRP Complexity
BGP supports many different address families and their purposes, use cases, and configuration, making in real-life BGP much harder to configure, troubleshoot and engineer compare to EIGRP networks.
BGP vs EIGRP Policy Support
Another most important reason we choose BGP is when we need to deploy policy, its excellent policy support. This means, that if we want to engineer the traffic inbound or outbound, BGP gives us many tools to do it. EIGRP has only bandwidth and delay, which is used to calculate routing metrics, and it is used for the Outbound traffic engineering/path manipulation purpose only.
BGP vs EIGRP Resource Requirement
BGP if there are so many prefixes may require a lot of CPU and Memory. EIGRP runs a Dual algorithm for the best path selection and it is considered a much less CPU consumed protocol, even compared to OSPF''s SPF algorithm, the amount of prefixes that EIGRP needs to calculate the best path can be easily handled by the today's modern networking devices.
BGP vs EIGRP Extendibility
Both BGP and EIGRP are TLV-based protocols, thus both are considered extendible protocols. Similar to IS-IS, they don't require a new version of the protocol when IPv6 support is added to the protocols for example.
BGP vs. EIGRP IPv6 Support
Both BGP and EIGRP support IPv6 of course. BGP supports IPv6 as just a new BGP AFI, SAFI.
BGP vs EIGRP Convergence
From the network convergence point of view, BGP is always known as a slow converged protocol. But saying BGP is slow, is wrong. If we understand Network Convergence better, we have two types of convergence. Control plane convergence and Dataplane convergence. It is a huge topic and we have a separate very detailed Network Convergence Course on the website.
But overall, Data plane convergence is Fast Reroute and with the BGP PIC feature, BGP can support Fast Reroute, thus, it can converge so fast too. Thus, maybe saying BGP Control plane convergence might be slow, due to a number of prefixes, device hardware, BGP TCP input queue, whether there is BGP RR or Full mesh, and many factors. Although there can be many other criteria to compare EIGRP vs BGP, for this blog post, I think it is enough. If you want to more about it, you can take our BGP course or you can check many of our free blog posts on this topic.