Subnetting
This is a skill that is required across a variety of CCNA topics and questions. Subnetting is required to configure network interfaces, troubleshoot network problems and read a routing table. You should know how to distinguish between classful and classless addressing, and when to apply subnet masks or wildcard masks.
In fact, subnet masks and wildcard masks affect what routes are advertised from a routing protocol to neighbor routers . Learn binary to decimal conversion and how to create your own class C subnetting table for quick reference. Consider as well that DHCP, DNS and NAT are all network addressing services.
Troubleshooting
Troubleshooting is a learned skill that draws on your knowledge of CCNA networking concepts. You have to learn a strategy or approach as well to trace and isolate network errors through root cause analysis.
Consider as well that knowledge of all topics on this top ten list are required for proper troubleshooting. Learn root cause analysis, all of the core IOS commands and protocol operation as a starting point.
Routing Protocols: EIGRP, OSPF, RIP
There are several layers of knowledge with OSPF, EIGRP and RIP routing protocols and significant coverage on the exam. Know how to do basic configuration, verify your configuration and troubleshoot neighbor connectivity.
The protocols share similar operational rules however there are differences that affect your troubleshooting approach. Know how administrative distance, metrics and neighbor adjacency are different for each protocol. Understand the differences between distance vector and link state routing protocols and where each is most suitable for deployment.
Access Control Lists (ACL)
When it comes to the CCNA exam, learn as much as you can about all types of ACLs. There are four groups: standard ACL, standard named ACL, extended ACL and extended named ACL. They are so prevalent on routers and firewalls that you have to know basic configuration of an ACL and also how to apply them correctly.
ACLs affect how traffic filtering works and is key to application layer troubleshooting. Any ACL requires a filter command along with a direction and network interface as primary attributes to permit or deny traffic.
Route Selection
Do you know how to read a routing table and how a route is selected to a destination subnet? This is a key aspect of troubleshooting when a question asks – why can’t a host access an application on a server. You would as part of your troubleshooting approach, list the routing table on a router and verify what if any routes exist to the server subnet.
So the question will test your knowledge of administrative distance, longest match rule and path metrics. Not to mention protocol operation for EIGRP, OSPF and RIP and rules for establishing network connectivity. One question will essentially test your knowledge of several different concepts.
Switch Trunking
Switch trunking requires that you first understand switch interfaces, VLANs, encapsulation and VLAN pruning. As a result the questions are really testing your knowledge of multiple switching concepts. Trunk interfaces are required to enable VTP domains as well.
Practically speaking all switches have trunk interfaces and they enable communication between multiple VLAN segments. DTP is a dynamic trunking alternative to static trunk interfaces with multiple modes that control when a trunk is established between switches.
Device Hardening
Not a surprise that passwords are on the top ten list of must know for the CCNA exam. In fact, CCNA security certification is becoming quite popular with the complexity of public internet connections and creativity of hacker attacks. The CCNA topics are basic and very reasonable testing your knowledge of initial setup and recommended commands for device hardening of routers and switches.
The primary topics include console security, enable passwords, VTY line access, password encryption and SSH. In addition there is configuration of local username accounts and passwords.
IOS Commands
CCNA simulation questions are worth 35% of all exam points and knowledge of IOS commands are a must for troubleshooting purposes. Most simulation questions are troubleshooting-based however some ask you to configure protocols or verify operational state. The following are a core group of IOS commands that you should know.
- show running-config
- show ip interface brief
- show ip interface
- show ip route
- show interfaces trunk
- show vlan
- show ip ospf neighbor
- show ip eigrp neighbors
- show access-lists
- show ipv6 [command]
- ping
- traceroute
Don’t forget as well that IPv6 changes the IOS command slightly. For example show ip route for IPv4 displays all routes based on IPv4 addressing. Any IPv6 routes in the routing table are displayed with show ipv6 route. You have to use both commands when there are IPv4 and IPv6 interfaces.
Ping and traceroute are industry standard tools and also much required for the CCNA exam. Cisco CLI has an excellent help facility ? to lookup commands that you forget or do not know.
Static Routing
Most routers will have at least one routing protocol enabled to advertise local subnets and receive routes from neighbors. Most routers are going to have some static routes for a variety of purposes. There is some additional maintenance and complexity that goes along with any dynamic routing protocols.
Static routes also include default routes and floating routes common to most configurations. Most internet connections from a branch office will require only a default route. You have to know static routing to read a routing table and understand how they affect route selection.
IPv6 Addressing
This is a somewhat new network addressing schema and not as well understood as older IPv4 addressing. Cisco realizes that the depletion of IPv4 address space and advent of IoT with billions of new access devices make knowing IPv6 high up on the list. There are a lot of differences between IPv4 and IPv6 that can trip you up when troubleshooting or configuring routing protocols.
Firstly there are multiple types of IPv6 addresses and route types. IPv6 address allocation is different from IPv4 and IOS commands are changed (only slightly however). You have to learn how to configure 128 bit addressing that is hexadecimal and create subnets based on the new address schema. Start with IPv6 addressing rules and review how routing protocols are enabled with single and multiple interfaces.
