Tauseef FayyazA to Z
Glossary
Every concept in this sheet, plus the smaller terms it uses. Select a concept to open its card.
A
- ARP
- The IPv4 protocol that finds the MAC address for an IP address on the local network by broadcasting a question and caching the answer.
C
- CDP and LLDP
- Discovery protocols that let directly connected devices announce their name, model, port and address.
- Common port numbers
- The numbers that identify a service on a host.
D
- DHCP and DHCP relay
- DHCP hands clients an address, mask, gateway and DNS servers through Discover, Offer, Request, Acknowledge.
- DNS records
- DNS turns names into addresses.
E
- EtherChannel and LACP
- Bundling several physical links into one logical link.
I
- Inter-VLAN routing
- Hosts in different VLANs need a router to talk.
- IPv4 addresses and CIDR prefixes
- An IPv4 address is 32 bits written as four numbers from 0 to 255.
- IPv6 addressing
- IPv6 addresses are 128 bits written in hex groups, such as 2001:db8:10::1/64.
M
- MAC address table
- The switch table mapping each MAC address to the port it was last seen on.
O
- OSI and TCP/IP models
- Two ways to split networking into layers.
P
- PortFast, BPDU Guard and Root Guard
- PortFast puts an access port straight into forwarding.
S
- Spanning Tree Protocol
- STP stops loops in a switched network by electing a root bridge and blocking redundant paths.
- Subnetting table
- The prefixes you meet most, with their masks, block sizes and usable hosts.
T
- TCP vs UDP
- The two main transport protocols.
- Trunks and 802.1Q
- A trunk carries many VLANs over one link by adding a 4-byte 802.1Q tag with the VLAN number to each frame.
V
- VLAN
- A VLAN splits one switch, or many, into separate Layer 2 networks.
- VLSM
- Carving one block into subnets of different sizes, largest first, so each LAN, link and loopback gets only the addresses it needs.