CCST Networking flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

OSI Layer 3

The network layer, which handles logical addressing and routing of packets between subnets. IP operates here, and routers make forwarding decisions using destination IP addresses.

TCP three-way handshake

The connection setup sequence SYN, SYN-ACK, ACK that synchronizes sequence numbers before data flows. It confirms both hosts are reachable and ready to exchange segments.

UDP characteristics

Connectionless transport with no handshake, acknowledgment, or retransmission. It has low overhead and is used by DNS queries, DHCP, TFTP, and real-time voice or video.

EtherType field

A 2-byte field in an Ethernet II frame that identifies the encapsulated protocol, such as 0x0800 for IPv4 or 0x86DD for IPv6.

MAC address OUI

The first 24 bits of a 48-bit MAC address, assigned to a vendor by the IEEE. It identifies the manufacturer, while the remaining bits are card-specific.

RFC 1918 private ranges

The reserved IPv4 blocks 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. They are not routed on the public internet and require NAT for internet access.

TTL field

An IPv4 header value decremented by each router; a packet reaching zero is dropped and ICMP Time Exceeded is returned. Traceroute exploits this behavior.

Hosts per subnet formula

For a subnet with h host bits, usable addresses equal 2^h minus 2. The two excluded addresses are the subnet (network) address and the directed broadcast address.

/26 subnet mask

A 26-bit mask written 255.255.255.192. It leaves 6 host bits, giving 64 addresses per block and 62 usable hosts.

Block size calculation

Subtract the interesting-octet mask value from 256 to get the block size. Subnet boundaries increment by that value, for example 256 minus 192 equals 64.

Broadcast address

The address in a subnet with all host bits set to 1. Frames sent to it reach every host in that subnet, and it cannot be assigned to a device.

IPv6 double colon rule

The :: notation compresses one run of consecutive zero groups. It may appear only once in an address, otherwise the original address could not be reconstructed.

IPv6 link-local address

An address in fe80::/10 automatically configured on every IPv6 interface. It is used for neighbor discovery and is never routed beyond the local link.

APIPA address

A 169.254.x.x address self-assigned when DHCP fails. Its presence usually indicates the client could not reach a DHCP server.

Default gateway role

The router address a host sends traffic to when the destination is outside its own subnet. Without a correct gateway, remote networks are unreachable.

Cat6a cable rating

Twisted-pair cabling rated for 10 Gbps to 100 meters at up to 500 MHz. It has stricter crosstalk specs than Cat6, which reaches 10 Gbps only to 55 meters.

T568B pinout

The wiring standard with white-orange, orange, white-green, blue, white-blue, green, white-brown, brown on pins 1 through 8. T568A swaps the orange and green pairs.

Single-mode fiber

Fiber with a small core that carries one light path, allowing very long distances at high bandwidth. It typically uses laser optics and costs more than multimode.

PoE 802.3at

PoE+ standard delivering up to 30 W at the power sourcing equipment. It powers devices such as access points and cameras over the same Ethernet cable.

Auto-MDIX

A switch feature that detects and corrects transmit and receive pin pairs automatically. It makes straight-through cables work regardless of whether devices are alike or unlike.

Switch versus hub

A switch forwards frames only to the port holding the destination MAC, creating per-port collision domains. A hub repeats every frame out all ports.

802.1Q trunking

A standard that inserts a 4-byte tag with a VLAN identifier into Ethernet frames. It lets one link carry traffic for multiple VLANs between switches.

Spanning Tree Protocol

A Layer 2 protocol that blocks redundant paths to prevent switching loops. It elects a root bridge and selects one forwarding path per segment.

DHCP DORA process

The four-step lease process: Discover broadcast, Offer from server, Request from client, and Acknowledge from server. The client then receives IP, mask, gateway, and DNS.

OSPF routing protocol

A link-state interior gateway protocol that builds a topology database and runs shortest-path calculations. It uses cost based on bandwidth and converges faster than RIP.

NAT versus PAT

NAT maps private addresses to public ones one-to-one. PAT, also called NAT overload, shares a single public address by tracking distinct source port numbers.

DNS A record

A resource record mapping a hostname to an IPv4 address. The AAAA record performs the same mapping for IPv6 addresses.

VLAN access port

A switch port assigned to exactly one VLAN, carrying untagged frames. Devices on it belong to that VLAN's broadcast domain.

ipconfig /flushdns

A Windows command that clears the local DNS resolver cache. It is used after record changes to force fresh lookups.

tracert command

A tool that sends packets with increasing TTL values to list each router hop. It shows where delay or packet loss begins along the path.

Duplex mismatch symptoms

One side full duplex and the other half duplex causes late collisions, CRC and alignment errors, and poor throughput. Fixing it usually means setting both sides the same.

nslookup utility

A command-line tool that queries DNS servers to test name resolution. It can request specific record types and compare answers from different servers.