Most community write-ups stop at the set community line. This one follows the tag all the way through: R1 tags a prefix with 65001:200 and no-export, R2 prints the community and flags it as not advertised to EBGP peer, and R3 answers with % Network not in table. Captured on IOS XE 17.18.2 in CML.
Route maps are the primary BGP traffic engineering tool on Cisco IOS XE. Match on AS-path, community, or MED, then set attributes to steer paths. A practical guide to matching, setting, and manipulating BGP routes.
RPKI lets prefix owners sign ROAs that say which AS is authorized to originate their prefixes. Route Origin Validation rejects invalid routes. A practical guide to RPKI and ROV on Cisco IOS XE for internet-facing networks.
BGP was designed when every AS was trusted. Accidental route leaks and deliberate prefix hijacks have caused repeated major outages. How to detect them, prevent them, and protect your AS from the blast radius when others make mistakes.
Default BGP convergence can take 3 minutes to notice a dead peer. That is fine on the public internet and unacceptable in enterprise or data center BGP. Every knob for reducing BGP failover time on Cisco IOS XE, including BFD.
You set local-pref, route maps, and communities, and traffic still goes the wrong way. BGP is deterministic; a surprise path means either policy is not applied where you think, or a higher priority step decided first.
Service provider BGP operates at a scale that dwarfs enterprise: full tables, hundreds of peers, thousands of routers. An SP BGP design guide covering peering relationships, policy, iBGP scaling, and transit economics.
Enterprise BGP design comes down to how many ISPs, how many borders, full table or defaults, and active-active or active-standby. From single-homed to multi-homed with traffic engineering, and when you do not need BGP at all.
This is the capstone article: a comprehensive pre-deployment checklist covering all STP hardening requirements. Organized by switch role, this checklist ensures your campus network STP implementation is secure, predictable, and ready for production traffic.
Troubleshooting STP requires knowledge of dozens of show and debug commands. This article provides a reference for every relevant command in Cisco IOS XE, with annotations explaining what each output means and when to use it.
The STP root bridge and the HSRP/VRRP active gateway should reside on the same switch. When they don't, traffic flows upstream to one switch and returns via another, wasting bandwidth and causing asymmetric path problems. This article covers alignment strategy and verification.
In a three-layer campus, STP topology must align with the physical hierarchy. This article shows how to place root bridges, design inter-layer redundancy, and troubleshoot anomalous topologies created by misconfiguration across access, distribution, and core layers.