BFD: Bidirectional Forward Detection

💡 BFD stands for Bidirectional Forwarding Detection

BFD is a Layer 3 protocol used to detect link failures super fast ⚡

It works with dynamic routing protocols — and even with static routes!

🛠 Why use BFD?

Let’s take OSPF as an example:

🕒 By default, OSPF sends Hello packets every 10 seconds, with a Hold timer of 40 seconds.

Of course, you can make it faster:

int e0/0

ip ospf hello-interval 1

But what if you want it even faster? 🚀

That's where BFD shines — you can go down to 50 milliseconds! 🧨

🔧 Configuration Examples:

1️⃣ With OSPF:

router ospf 1

bfd all-interfaces

exit

int e0/0

bfd interval 50 min_rx 50 multiplier 3

exit

✅ This way, if the BFD timer expires, OSPF will immediately know the neighbor is gone.

No need to wait 40 seconds — break the relationship now!

2️⃣ With Static Routes:

int e0/0

bfd interval 50 min_rx 50 multiplier 3

exit

ip route static bfd e0/0 10.2.0.1

ip route 1.1.1.1 255.255.255.255 e0/0 10.2.0.1

This configuration ensures that BFD monitors the static route via the specified interface and next-hop.

🧪 To verify the BFD neighbor relationship:

show bfd neighbors

show bfd neighbors detail

✅ And that wraps up our BFD article!

Thanks for reading — I hope it helped clarify how BFD protects your Layer 3 links 💪