IT Support, Networking and Infrastructure · Networking fundamentals
Routing, switching and Cisco networks
Once a network outgrows a single room, somebody has to decide how traffic moves between its parts and what happens when a link fails. That is routing and switching: dividing with VLANs, preventing loops, choosing paths and translating addresses at the edge. A large share of enterprise networks run on Cisco equipment, which is how the CCNA became the reference exam for this work, but the ideas hold on any vendor's kit.
Why this topic exists: VLANs, spanning tree, static and dynamic routing: CCNA's Network Access (20 %) and IP Connectivity (25 %) domains, with NAT in IP Services, and the daily work of a network engineer.
A network engineer spends most of the week inside two kinds of device. Switches forward frames within a segment by learning which hardware address sits behind which port; routers forward packets between segments by consulting a table of destinations. The engineering begins when a network needs more than the defaults: splitting one switched network into several VLANs so that finance and guest devices never share a broadcast domain, joining those VLANs through a router or a switch that can route, and deciding which routes are typed in by hand and which are learned from a protocol such as OSPF.
What the CCNA builds, in order
- Access. Create VLANs and the trunks that carry several of them between switches, and explain how spanning tree blocks redundant links so frames cannot circle forever.
- Wireless attachment. Recognise how access points and their controllers connect to the switched network, which is why the CCNA files wireless under network access.
- The routing table. Read it entry by entry, work out which one wins for a given destination, and configure static routes, a default route among them.
- Dynamic routing. Bring up single-area OSPF, understand how neighbours form, and explain why a route does or does not appear.
- Edge services. Configure NAT so private addresses can reach the internet, alongside the other IP services such as DHCP relay and time synchronisation.
Network Access and IP Connectivity together are the heaviest part of the exam, and the weighting mirrors the job: engineers spend far more hours on VLAN changes and missing routes than on anything else. Cisco's exam page states that the current version, v1.1, can be sat until 2 February 2027 and that v2.0 starts the next day, so anyone beginning preparation now should check which blueprint their material follows.
Beyond the associate level
The core paper of CCNP Enterprise takes the same subjects into campus design, redundancy, virtualisation and assurance, and adds a concentration exam chosen by the candidate. Network work is also turning into code. Devices expose APIs, and configurations are generated and checked by scripts rather than typed port by port, which is the territory of CCNA Automation and of the silo's scripting and automation topic. Engineers who only ever configure at the command line will still find work, though fewer of the interesting roles. Choosing which traffic may cross these paths belongs to network security, and the virtual networks cloud providers sell, with their own names for familiar ideas, sit under cloud.
The outage new engineers cause most
A switching loop. A second cable is patched in for 'resilience', or spanning tree is disabled on a port so a device comes up faster, and broadcast frames begin circling without end until the whole segment stops answering. Before changing anything on a switch, know which ports are protected and why, and never remove a protection because a device was slow to connect.
Next to this topic
Concepts to know
Glossary entries with the reason each one matters here.
Certifications that test it
Vendor exams and free certificates; facts, cost and the preparation path are on each page, and the certifications hub has them all.
Tools of the trade
- Cisco Packet Tracer
The simulator most CCNA lab work runs in.
Frequently asked
- Do I need real Cisco equipment to prepare for the CCNA?
- No. Cisco's Packet Tracer simulator covers most of the syllabus, and Cisco Modeling Labs runs real device images for the rest. Second-hand switches help with cabling and console access, but they are a convenience rather than a requirement.
- Is routing and switching still relevant now that so much runs in the cloud?
- Yes. Offices, campuses, factories and data centres still run on physical switches and routers, and cloud networking reuses the same ideas of subnets, routes and address translation under different names. An engineer who understands the physical version learns the cloud version quickly; the reverse is harder.
- What comes after the CCNA?
- Usually either CCNP Enterprise, for depth in campus and enterprise networks, or a move toward automation, for which CCNA Automation is the associate paper. Some engineers turn toward security instead and take network security as their next field.
Courses in the directory
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Last reviewed 26 September 2026 · Getting Digital