OSPF
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OSPF Filtering: area range vs filter-list vs distribute-list vs summary-address
OSPF gives you four different ways to stop a prefix from getting somewhere, and they are not interchangeable. Two of
Labs
Hands-on Cisco IOS XE lab walkthroughs. Each lab ships with a real CML topology, configs you can paste, and verified show output. Articles tagged Labs cover the full CCNA 200-301 blueprint across Network Fundamentals, Network Access, IP Connectivity, IP Services, and Security Fundamentals.
Latest
OSPF
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The OSPF Forwarding Address: Why Your Type 5 Route Goes the Wrong Way
Here is a routing puzzle. An OSPF router has a route to an external network. The route is in the
OSPF
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OSPF Stub Router: max-metric router-lsa and Graceful Maintenance
You need to reload a core router. It is carrying live traffic. The naive approach - just reload it - drops every
OSPF
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OSPF Prefix Suppression: Shrinking the Routing Table
Look at your routing table and count how many of those prefixes anyone actually sends traffic to. In a typical
OSPF
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OSPF SPF and LSA Throttling Timers: Tuning Convergence Safely
OSPF converges fast. That is its whole reason for existing. But "fast" is a tuning decision, and the
BGP
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Expert BGP Troubleshooting: Five Broken Scenarios, Ticket Style
The CCIE troubleshooting section does not ask you to explain BGP. It hands you a broken network and a clock.
BGP
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IPv6 over BGP: MP-BGP for IPv6 and 6PE Explained
Here is a problem that a great many service providers had, and some still have: a fully working, fully tuned,
BGP
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BGP Multipath and Load Sharing: eBGP, iBGP, and eiBGP
BGP installs one best path. That is the default and it is deliberate: BGP is a policy protocol, and the
BGP
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Designing BGP Policy with Communities: A Practical Framework
Most networks use BGP communities the way most people use a junk drawer: things get put in, nobody agrees what
BGP
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BGP Route Dampening: Penalties, Half-Lives, and Why It Fell Out of Favor
Dampening penalises a prefix for flapping and refuses to use it even after it recovers. Captured live on CML with IOS XE 17.18.2: penalty 2818 from three flaps, the prefix held at *d while an identical prefix from the same neighbor stays best, plus the advertisement-interval gotcha that makes...
BGP
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BGP Outbound Route Filtering (ORF): Pushing Your Filters to the Neighbor
Inbound prefix filtering is normal hygiene: you accept the routes you want and drop the rest. But think about what
BGP
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BGP Conditional Advertisement: advertise-map, exist-map, and non-exist-map
Every dual-homed network eventually asks the same question: how do I keep a backup path truly idle until I