A complete guide to IS-IS: NSAP/NET addressing, Level-1/Level-2 hierarchy, PDUs and TLVs, adjacency formation, DIS election, LSP flooding, metrics, SPF/PRC, route leaking, authentication, IPv6 and multi-topology, modern extensions (TE, Segment Routing, Flex-Algo), an IS-IS vs OSPF comparison, and working configs for Cisco IOS-XE, IOS-XR and FRRouting.
Part 4 of the BGP series for CCNP ENCOR 350-401 v1.2: the complete 13-step best path selection algorithm with a worked tie-break at every level, the two validity gates that run before step 1, the MED comparison rule that catches everyone, hot potato routing, multipath, and four hands-on labs.
Part 3 of the BGP series for CCNP ENCOR 350-401 v1.2: the four ways to originate a prefix, why the network statement needs an exact mask match, the iBGP next-hop problem and next-hop-self, the four path attribute categories, and how weight, local preference, AS_PATH, origin, MED and communities differ in scope — with four hands-on labs.
Part 2 of the BGP series for CCNP ENCOR 350-401 v1.2: TCP 179, the six-state finite state machine, the five message types, timer negotiation, eBGP multihop versus TTL security, MD5 authentication, and a four-layer troubleshooting method with four hands-on labs.
Part 1 of a four-part BGP series for CCNP ENCOR 350-401 v1.2: why BGP is a policy protocol rather than a metric protocol, autonomous systems and ASN ranges, the rules that separate eBGP from iBGP, the iBGP full-mesh and next-hop problems, BGP's three tables, and four hands-on labs with answers.
Full password recovery procedure for a Cisco Catalyst 9200 running IOS-XE, using the ROMMON SWITCH_IGNORE_STARTUP_CFG variable — with console captures, the correct command order, how to clear the ignore flag, and the pitfalls that leave a switch booting with no configuration.
A full walk through Quality of Service for CCNP ENCOR 350-401 v1.2 topic 1.4: the four impairments, DiffServ marking and PHBs, the six QoS components, MQC policy design, Catalyst switch implementation, worked bandwidth and token-bucket maths, and five hands-on labs with answers.
The finale: a safe bulk config-push tool that previews a per-device diff, gates the commit behind confirmation, and reports what changed — plus where to take Python next.
A complete config-backup tool: read a YAML inventory, pull running-configs with Netmiko, save to disk, and commit to Git so every change becomes a reviewable diff.
Turn show command output into lists of dicts with TextFSM and ntc-templates — parse_output for common commands, hand-written templates for the rest, no regex per command.