OSPF for ISPs
Your ISP's IGP is what holds everything together: BGP, MPLS, management. Badly designed OSPF turns into adjacency flap loops and instability across the whole backbone.
What OSPF is
OSPF is a link-state Interior Gateway Protocol (IGP) that computes the shortest path between routers inside the same AS. Unlike BGP (between ASes), OSPF resolves internal topology: how a packet gets from PoP X to PoP Y inside your network.
It's the de facto standard in mid-sized Brazilian ISP backbones. IS-IS is an alternative for very large networks — but OSPF covers 95% of cases.
What RASYS does with OSPF
- Area design — well-sized area 0 (backbone), stub/totally-stub areas where they make sense to reduce LSA flooding.
- Metrics and cost — manual cost to force preferred path (fiber link vs. radio). Avoid OSPF preferring sub-optimal route from auto-bandwidth bugs.
- BFD (Bidirectional Forwarding Detection) — adjacency failure detection in milliseconds instead of seconds. Sub-second failover convergence.
- OSPFv3 for IPv6 — dual operation with OSPFv2, no doubled overhead.
- BGP redistribution — which internal routes should appear in iBGP/eBGP and vice-versa, with filters to avoid import-export loops.
- Authentication — MD5/SHA between neighbors to prevent LSA injection from unauthorized equipment.
- Troubleshooting — adjacencies stuck in INIT/EXSTART/LOADING, LSA debug, Graceful Restart during maintenance.
Equipment we work with
Huawei NE/AR series, Juniper MX/QFX, Cisco IOS/IOS XR/NX-OS, Mikrotik RouterOS, FRR/Quagga on Linux.
When it makes sense to talk to us
You're growing and area 0 is huge; convergence is slow and customers complain; adjacencies keep dropping with no clear reason; want IPv6 in IGP without touching IPv4; consolidating two networks after acquisition.
Talk to us. See also: BGP, MPLS, OSPF in glossary.