This is the hands-on half of our OSPFv3 coverage: a complete dual-stack configuration on Cisco IOS XE, from ipv6 unicast-routing to verified end-to-end reachability, with every capture from a live CML lab. If you want
OSPFv3 is not "OSPF with longer addresses". It is a redesign of the protocol machinery that happens to have shipped alongside IPv6, and with address families (RFC 5838) it can carry IPv4 routes too, which surprises almost everyone
Routing protocols detect dead neighbors with hello timers measured in tens of seconds. Modern applications notice outages measured in hundreds of milliseconds. BFD (Bidirectional Forwarding Detection) closes that gap: a lightweight, protocol-agnostic liveness check that runs in the forwarding
One router, multiple routing tables. That is the entire idea behind VRF (Virtual Routing and Forwarding), and it is the foundation of everything from enterprise network segmentation to service provider L3VPNs. VRF-Lite is the version without MPLS: no label
Routing protocols answer one question: what is the best path to this destination? Policy-based routing (PBR) exists for every time that is the wrong question. Send this application out the backup circuit. Keep guest traffic off the MPLS link.
Two-point redistribution is where redistribution stops being a config exercise and starts being a design problem. The moment two border routers both translate between routing domains, every prefix has a feedback path: out through one door, around the block,
Most networks do not run one routing protocol. Mergers bolt an EIGRP shop onto an OSPF backbone, a campus hands off to a service provider running BGP, or a legacy site keeps RIP alive years past its expiry date. Route
The neighbors are up, the interfaces are clean, and yet a route that should be in the table simply is not. Missing-route problems are sneakier than adjacency problems because nothing is visibly broken; the protocol is running exactly as
Two routers, two broken adjacencies, one log message. Real CML captures on IOS XE 17.18.2 show the %DUAL-5-NBRCHANGE K-value mismatch that repeats every few seconds, the AS mismatch that logs absolutely nothing, and what both look like the moment they recover.
Advertising every route to every neighbor is the default, not a requirement. Sometimes a spoke should never learn the DMZ prefixes, a lab block should stay invisible to production, or a partner connection should see exactly three networks and nothing
If you have ever looked at show ip eigrp topology on a modern router and wondered why the metrics suddenly have nine or ten digits, you have met wide metrics. Named mode EIGRP replaced the classic 32-bit composite metric
A route in Active state with a reply outstanding, captured live on IOS XE 17.18.2 in CML: the r and rs status flags that name the silent neighbor, why packet loss gives you neighbor flaps instead of SIA, and why modern IOS XE usually logs retry limit exceeded before it ever prints %DUAL-3-SIA.