ip route: Managing the Linux Routing Table
Every field in a route line, get against show, blackhole routes, the replace gotcha, and policy routing with multiple tables.
IP Routing
The routing half of the CCNP and CCIE blueprints. Articles tagged IP Routing cover static and dynamic routing, redistribution, policy routing and route manipulation on Cisco IOS XE.
Latest posts
IGP Migration: Moving from EIGRP to OSPF Without an Outage
Migrate a live network from EIGRP to OSPF without dropping a packet: run both protocols side by side, then flip administrative distance one command at a time. The ships in the night technique with real lab output.
Multi-Protocol Redistribution: The CCIE Scenarios That Break Networks
Two-point redistribution is where networks go to die. This article builds the classic CCIE failure for real in a CML lab, shows a route being re-injected into the protocol it came from, and then fixes it with the exact output at each step.
Object Tracking and Reliable Static Routes with IP SLA
A static route stays in the table as long as the interface is up, even when the path is dead. This post pairs object tracking with an IP SLA probe to build a static route that tests the path, then kills the path to prove it works.
Troubleshooting Route Redistribution: Missing, Looping, and Suboptimal Routes
Redistribution fails three ways: routes that never arrive, routes that echo back and loop, and routes that arrive but take the long way. All three captured on CML with IOS XE 17.18.2, including the EIGRP external at AD 170 that loses to OSPF's 110 while the shorter direct path sits unused in the...
OSPFv3 Configuration on Cisco IOS XE
A complete dual-stack OSPFv3 configuration on Cisco IOS XE, from ipv6 unicast-routing to verified end-to-end reachability, with every capture taken from a live CML lab.
OSPFv3 Explained: OSPF for IPv6 (and Address Families for IPv4)
OSPFv3 is a protocol redesign, not OSPF with longer addresses, and with address families it carries IPv4 too. See what changed from OSPFv2, what stayed identical, and what it looks like on the wire in a live Cisco IOS XE lab.
BFD: Sub-Second Failure Detection for OSPF, EIGRP, and BGP
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 on Cisco IOS XE: Configuration and Verification
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.
Policy-Based Routing (PBR): Configuration and Verification
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.
Redistribution Loop Prevention: Route Tags, AD, and Filtering
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 on Cisco IOS XE: The Complete Multi-Protocol Guide
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.