Build a Multi-Protocol ISP Topology with OSPF and BGP Using FRRouting

FRRouting (FRR) is an open-source Internet routing protocol suite for Linux that implements BGP, OSPF, IS-IS, RIP, and other protocols. Network engineers at Internet Service Providers use these protocols together to build scalable, resilient networks -- OSPF handles internal routing within the provider backbone while BGP manages route exchange with customers and upstream peers.

In real ISP networks, the separation between interior and exterior routing is fundamental. OSPF (or IS-IS) builds a topology map of internal routers and computes shortest paths, while BGP carries customer prefixes and applies routing policy through prefix-lists, route-maps, and communities. Route redistribution bridges these two worlds, injecting selected BGP routes into OSPF and vice versa.

In this lab, you will deploy 5 Ubuntu VMs running FRRouting on Azure, each configured as a router in a mini-ISP topology. You will configure OSPF Area 0 across the backbone routers, establish eBGP peering with customer routers, set up route redistribution between OSPF and BGP, and apply prefix-list filtering to control which routes are advertised.

Objectives

Upon completion of this advanced level lab, you will be able to:

• Deploy and verify a 5-router FRRouting topology on Azure VMs
• Configure OSPF Area 0 across the ISP backbone using vtysh CLI
• Establish eBGP peering between core and customer edge routers
• Configure route redistribution between OSPF and BGP with route-maps
• Apply prefix-list filtering to control route advertisements
• Verify end-to-end reachability between customer loopback networks

Who is this lab for?

This lab is designed for:

• Network engineers learning ISP routing operations
• CCNA and CCNP certification candidates
• Infrastructure teams transitioning from hardware routers to software-defined routing
• Anyone building hands-on experience with BGP and OSPF configuration