IPv6 First-Hop Security Part 1: RA Guard and DHCPv6 Guard
In IPv4, a rogue DHCP server is a nuisance you can contain with DHCP snooping. In IPv6, the equivalent threat
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
Unicast RPF: Strict vs Loose Mode
Source IP addresses are trivially forged. Nothing in the IP header proves the source is who it claims to be,
Control Plane Policing (CoPP): Protecting the CPU
Every router has a CPU, and that CPU is a shared, finite resource that both keeps the network running (OSPF
AAA on Cisco IOS XE: TACACS+ vs RADIUS for Device Administration
The moment more than one person can log into your routers, you have an access-control problem. Who is allowed
Conditional Debugging on Cisco IOS XE: Debug Without Melting the Box
There is a particular kind of fear that stops engineers from using the most powerful troubleshooting tool on a Cisco
DHCPv6 Explained: Stateful, Stateless, SLAAC, and the Relay
IPv6 host addressing is where a lot of otherwise competent engineers quietly lose confidence, because there are three mechanisms that
SPAN, RSPAN, and ERSPAN: Packet Mirroring on Cisco Switches
Eventually every network problem reaches the point where you have to see the actual packets. Counters lie by omission, logs
Object Tracking and Reliable Static Routes with IP SLA
A static route has one fatal flaw: it believes in itself. As long as the outgoing interface is up, the
IP SLA on Cisco IOS XE: Probes, Thresholds, and Tracked Failover
IP SLA answers "is this path usable," which is not the same question as "is this link up." Captured on CML with IOS XE 17.18.2: ICMP and jitter probes against a deliberately degraded link, then a full tracked failover with the SLA timing out, %TRACK-6-STATE logging the object down, and the...
Flexible NetFlow on Cisco IOS XE: Records, Monitors, and Exporters
NetFlow answers the question your monitoring dashboard cannot: not "is the link busy" but "who is making
MPLS
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Troubleshooting MPLS L3VPN: Where VPN Routes Go Missing
An MPLS L3VPN route makes a long journey. It starts as an IP prefix in a customer's routing
MPLS
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Troubleshooting MPLS LDP: "unusable: no label" and Broken LSPs
MPLS forwarding runs on labels, not on IP reachability, so a dead LDP session leaves every green light green while the customer blackholes. Captured on CML with IOS XE 17.18.2: the unusable: no label CEF entry, the full LDP LIB, a hop-by-hop walk to find where the binding stops, and No Label...