Layer 2 switching boils down to one mechanism: the CAM table (Content-Addressable Memory), also called the MAC address table. The switch builds it dynamically by reading the source MAC of every frame it receives and noting which port that
IPv6 static routes look almost identical to IPv4 static routes. There is one wrinkle worth knowing: when you use a link-local address as the next-hop, you MUST specify the exit interface, because link-local addresses are scoped per-
When the network breaks, the engineer who fixes it first is the one with a method. Trial-and-error works on the third try. A systematic approach to localizing the fault works on the first. This lab teaches you to
GRE - Generic Routing Encapsulation - is the lightest-weight tunnel encapsulation in widespread use. It takes an IP packet, wraps it in another IP packet plus a small GRE header, and ships it across whatever underlay routing happens to exist. No
PPP - Point-to-Point Protocol - is the WAN encapsulation that survived. Frame Relay died, X.25 died, ATM mostly died, but PPP is still on every serial WAN link, every dial-up backup, every long-haul leased line that has
Every IP packet on the planet starts and ends with two 32-bit numbers - the source and destination addresses. CCNA gives you the structure to read those numbers, decide what is local and what is remote, and what your router
A static route on a Cisco router can be written two ways: with a next-hop IP address, or with an exit interface. The two forms LOOK almost identical in the running-config but they cause different forwarding behavior, different
ARP - the Address Resolution Protocol - is the unsung mechanism that makes Layer 3 routing actually work over Layer 2 Ethernet. Every time your router forwards a packet on a LAN, ARP is what tells it which MAC address to write
IPv6 has been "the new thing" for so long that engineers sometimes forget it is now the default address family on cloud platforms, mobile networks, and most modern ISPs. This lab teaches the structure of an IPv6 address:
The IOS XE command-line interface is the language you will type into every Cisco router in this library. Hundreds of commands, dozens of modes, one set of conventions that everyone in networking takes for granted but no one is
Standard access lists filter traffic based on source IP only. Numbered standard ACLs use IDs 1-99 and 1300-1999. They are the simplest filter on a Cisco router and a great introduction to the ACL concept: a list of
OSPF (Open Shortest Path First) is the link-state protocol that powers most enterprise networks. Single-area OSPF puts every router in Area 0 - the backbone - and is the simplest production-grade dynamic routing protocol you can deploy. This lab