Default hello timers take tens of seconds to notice a dead neighbor. This post configures BFD on Cisco IOS XE and races it against OSPF defaults: 34 seconds without BFD, 0.58 seconds with it, captured live with a stopwatch.
VRF-Lite gives one IOS XE router multiple isolated routing tables without MPLS or MP-BGP. This guide builds two VRFs, proves the isolation, then punches a deliberate, controlled hole between them with static route leaking.
PBR routes on source address, protocol, port, or size instead of destination alone. This post configures it on Cisco IOS XE, proves it with debug ip policy and route-map counters, and covers the failure modes.
Two border routers redistributing between the same domains give every prefix a feedback path. Build the forwarding loop live on Cisco IOS XE, capture it happening, then fix it with route tags the way production networks do.
Route redistribution end to end on Cisco IOS XE: how seed metrics work, what each protocol demands before accepting foreign routes, and what the routing table looks like at every stage. Every capture comes from a live CML lab.
Neighbors up but a route is missing? A systematic walk through the five places an EIGRP route can die on its way to the routing table, with real failure output from a CML lab.
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.
Filter EIGRP routes with distribute lists powered by prefix lists and route maps. Both flavors configured on a live CML lab, with before-and-after routing tables and the habits that keep filtering from becoming a mystery outage.
Named mode EIGRP replaced the 32-bit composite metric with a 64-bit version: delay in picoseconds, a scaling factor before the routing table, and quiet conversions at classic/named boundaries. Decoded with real CML output.
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.
Unauthenticated EIGRP forms adjacencies with anything that speaks the protocol. This post configures MD5 key chains and HMAC-SHA-256 in classic and named mode on a live CML lab, then breaks a key to show what failure looks like.
EIGRP is the only Cisco IGP that load balances across unequal-cost paths. This lab walks variance on live IOS XE: the topology table, the feasibility check, variance 2 in named mode, and the traffic share counters that prove the split.