An unauthenticated EIGRP interface will happily form an adjacency with anything that speaks the protocol. That means anyone who can plug into that segment can inject routes, blackhole traffic, or quietly become a man in the middle. Authentication closes that
Every routing protocol can load balance across equal-cost paths. EIGRP is the only IGP on Cisco routers that can load balance across unequal-cost paths, and the knob that unlocks it is a single number called variance. It is
Route summarization is one of those EIGRP features that looks like a simple address-shortening trick but quietly solves three different problems at once: it shrinks topology tables, it speeds up convergence, and it creates query boundaries that protect you
Sooner or later every engineer copies something onto or off a router: a config backup before a risky change, a new IOS image, a crash dump for TAC. The two classic transports are TFTP and FTP, they behave very differently,
DHCP hands a host its network identity; DNS makes names usable instead of addresses. The CCNA asks you to keep their roles straight and to configure a router as a DHCP server and relay, and the relay part is where
When something breaks at 3 a.m., the first question is "what changed, and when?" Syslog is the answer, but only if you set it up before the outage: severity levels chosen deliberately, messages shipped off-box to
SNMP is how monitoring systems actually know your interface went down, your CPU spiked, or your optics are running hot. Every NMS you will ever deploy (LibreNMS, Zabbix, SolarWinds, Catalyst Center's assurance features) speaks it. This article explains
Wrong time on a network device is not a cosmetic problem. Certificate validation fails, log timestamps become useless for incident correlation, and time-based authentication (like 802.1X with certificates, or API tokens) starts breaking in ways that look random.
NAT is the reason your private 10.x network can talk to the internet, and it is also one of the CCNA topics where the terminology trips up more people than the configuration. Cisco IOS XE gives you three flavors:
The CCNA v1.1 refresh added artificial intelligence and machine learning to the blueprint, and it is one of the few topics where the competition has not caught up yet. You are not expected to build models; you are expected
Once you accept that configuring devices one at a time does not scale, the next question is which tool does the configuring for you. The CCNA v1.1 blueprint names three configuration-management tools (Ansible, Puppet, Chef) and, with the
The command line is a conversation for humans. REST APIs are the conversation for programs, and once a controller sits in front of your network (see Controller-Based Networking and SDN), REST is how your scripts, dashboards, and automation tools