“There are two kinds of Network Engineers: those who have caused a network-wide outage, and those who will.”

I earn my badge at Spectranet. The task was simple: Redistribute a specific customer BGP block into OSPF.

The Mistake

I logged into the Core Router. My fingers flew.

router ospf 1 
 redistribute bgp 65000 subnets

I hit Enter.

I had forgotten the Route Map.

I told the router to take 500,000 Internet Routes and shove them into our internal OSPF database.

The Meltdown

OSPF is not designed for the internet table.

• T-10s: CPU spiked to 100%.
• T-30s: OSPF process crashed under the weight of Type-5 LSAs.
• T-60s: The network started flapping violently. Major outage.

I had effectively DDoS-ed our own control plane.

The Fix

I couldn’t issue a no redistribute because the CLI was unresponsive. I had to console in and hard-kill the BGP session.

clear ip bgp *

Once the CPU dropped, I applied the fix—the one line that would have saved me.

redistribute bgp 65000 subnets route-map FILTER_CUSTOMER_ONLY

Key Takeaway

Measure twice, cut once.

NEVER redistribute BGP into an IGP without a filter. OSPF cannot handle the internet table. If you don’t filter, you don’t just break the network—you melt the Core.