"Bgp At Doors of Autonomous Systems is Simple" - The official subject project name, and, also, a heroic mistruth.
BADASS is a network administration project in 42's post-cursus, building on the trauma knowledge gained through the NetPractice subnetting project in the cursus. Instead of simply calculating routes theoretically, the idea here is to simulate an actual network using GNS3 and Docker, configure routers and hosts, packet capture and inspection with Wireshark and progressively go down the rabbit hole of VXLAN, BGP, EVPN, OSPF and the general dark arts of making packets go where they are supposed to.
The project is split into three parts. The first involves setting up GNS3 with custom Docker images: one lightweight host image and one router image running the required routing daemons such as Zebra, BGPD, OSPFD and ISISD. The second part introduces VXLAN, first in static mode and then using multicast groups, allowing two distant hosts to behave as if they were sitting on the same local network, which is both very clever and slightly dishonest. The final part goes further by configuring a small datacenter-style Spine & Leaf topology using BGP EVPN, with OSPF as the underlay and a route reflector handling the sharing of MAC reachability information between the leaf routers.
In practice, this means configuring virtual routers, bridges, VTEPs, VXLAN interfaces, BGP neighbours, EVPN route types, Docker containers and GNS3 topologies, then using ping, packet captures, routing tables and vtysh commands to prove that the whole thing is not just decorative.
Part 1 is about getting GNS3 and Docker to play nicely together, creating a lightweight host image and a router image with the necessary routing daemons running inside it.
Part 2 introduces VXLAN, allowing two hosts to communicate as if they were on the same local network, despite being separated by routers. First this is done manually, then with multicast, which is basically the network finding its friends without being individually introduced.
Part 3 adds BGP EVPN, where the routers start sharing MAC address information through BGP instead of relying on static VXLAN configuration. The spine acts as a route reflector (magic mirror), the leaves act as VTEPs (tunnel endpoints), and once a host sends traffic, its MAC address gets advertised dynamically through the network.
The main take-away is that BGP is not just vague internet wizardry. It can also be used inside a virtual datacenter-style network to help machines find each other while VXLAN carries the traffic underneath.
- AS - Autonomous Systems
- GNS3 - Graphical Network Simulator 3
- BGP - Border Gateway Protocol
- EVPN - Ethernet Virtual Private Network
- VXLAN - Virtual Extensible LAN
- VTEP - VXLAN Tunnel Endpoint
- OSPF - Open Shortest Path First
- IS-IS - Intermediate System to Intermediate System
- FRR - Free Range Routing, like the chickens
- BGPD - BGP daemon
- OSPFD - OSPF daemon
- ISISD - IS-IS daemon
- SD - Sleep Daemon - wait nevermind
- VNI - VXLAN Network Identifier
- RR - Route Reflector
- MAC - Media Access Control
- LAN - Local Area Network
- UDP - User Datagram Protocol aka spray-and-pray
- TCP - Transmission Control Protocol aka registered post
- ICMP - Internet Control Message Protocol
- ARP - Address Resolution Protocol
- L2 - Layer 2 / Data Link Layer
- L3 - Layer 3 / Network Layer
They said networking was important in this career... is this what they meant?