Networking Fundamentals Flashcards
Layers of OSI Model
1 - Physical
2 - Data Link
3 - Network
4 - Transport
5 - Session
6 - Presentation
7 - Application
Ethernet frame
Preamble
Start frame delimiter
Destination MAC
Source MAC
EtherType
Payload
FCS
IP Packet header
Header
Source IP address
Destination IP address
Payload
TCP Header
Source Port
Destination Port
Sequence number
Acknowledgement number
DO
RSV
Flags
Window Size
Checksum
Urgent pointer
UDP Header
Source Port
Destination Port
Length
Checksum
TCP flags
SYN - synchronize, establish connection
ACK - acknowledge
FIN - finish
PSH - push, do not buffer
URG - urgent
RST - reject packet
MTU
maximum transmission unit - largest PDU size that can be sent in one transmission
Mesh topology
Multiple connections between nodes
Star/hub-and-spoke topology
All nodes connected to a central device (switch or hub)
Bus topology
All nodes connected to a central line (bus) that must be terminated at each end.
Ring topology
Each device is connected to two other devices on either side. Mostly unidirectional.
Hybrid topology
a combination of different types
Peer-to-Peer network
Each node is connected to each other acting as both server and client
Client-server
Client machines want to use resources; servers have these resources
LAN
Local Area Network
MAN
Metropolitan area network - a large network that connects machines in a local area - larger than a LAN but smaller than a WAN
WAN
Wide area network - spans a large area, connects multiple LANs together
WLAN
Wireless LAN
PAN
Personal area network - Bluetooth/NFC connected devices (headphones + headset, etc.)
CAN
Campus Area Network
SAN
Storage Area Network - a networked pool of storage devices that can be accessed by connected machines as though they were local drives
SDWAN
Software-defined Wide Area Network - Cloud-based software controls routing of data, rather than physical devices Instead of a central data center, these things are in the cloud.
MPLS
Multiprotocol label switching - routs traffic using labels instead of network addresses. Useful for connecting remote sites to each other through the cloud; can offer QoS; labels are “pushed” on to packets when they enter cloud and “popped” off when they leave.
mGRE
Multipoint Generic routing encapsulation. Used to dynamically link remote sites together (connections are established as needed and destroyed when finished).
Demarc
Demarcation point - where your equipment ends and the ISP’s begins
Smartjack
Can convert between signal types, buffer or regenerate signals, etc.
vSwitch
Virtual switch
vNIC
Virtual network interface card - NIC of a virtual server (or other machine)
NFV
Network function virtualization - replacing physical network devices with virtual versions; managed by a VMM (Hypervisor)
Satellite internet
wide coverage area but high latency
DSL
Uses old phone lines - tops out at 24 Mbps
Cable internet
Fast speed, wide availability
Leased line internet
fast dedicated fixed-bandwidth connection (usually fiber)
Metro-optical
Metropolitan ethernet connection
Cat 5 UTP
Max. distance: 100m
Max Bandwidth: 100 Mbps - 1 Gbps
Cat 5e UTP
Max. distance: 100m
Max Bandwidth: 1 Gbps
Cat 6 UTP
Max. distance: 55m
Max Bandwidth: 10 Gbps
Cat 6a UTP
Max. distance: 100m
Max Bandwidth: 10 Gbps
Cat 7 UTP
Max. distance: 100m
Max Bandwidth: 10+ Gbps
Cat 8 UTP
Max. distance: 100m
Max Bandwidth: 25 / 40 Gbps
Coaxial RG-6
Used for cable internet; has F-type connector; 75 Ohms
Twinaxial
2 inner conductors that share an outer conductor
TIA/EIA-568A
Green-white
Green
Orange-white
Blue
Blue-white
Orange
Brown-white
Brown
TIA/EIA-568B
Orange-white
Orange
Green-white
Blue
Blue-white
Green
Brown-white
Brown
Single-mode fiber
Uses lasers; typically yellow sheath
Multimode fiber
Uses LEDs; typically orange sheath
LC connector
ST connector
MTRJ connector
APC (fiber connection)
Angled physical contact
UPC (fiber connection)
Ultra Physical Contact (rounded tip)
RJ-11
smaller connector used for phone lines
RJ-45
larger connector for UTP/STP
F-Type connector
Used for coaxial cable
Media converters
used to convert one type of signal to another (fiber to copper, etc)
SFP
Small form-factor pluggable
SFP+
Enhanced version of SFP, can support up to 10 Gbit
QSFP
quad - SFP supports up to 40 Gbit
Patch panel
Cables come in from long runs, terminate at the back of patch panel. Patch cables are used to connect from panel to switches.
Fiber distribution panel
patch panel for fiber
66 punchdown block
used to connect phone lines (older)
110 punchdown block
newer punchdown block used for phone lines and network cables (up to cat5e)
Krone punchdown block
a type of punchdown block that uses several enhancements
Bix punchdown block
type of punchdown block
10BASE-T
10 Mbit
Baseband
Twisted pair
100 m max run
100BASE-TX
100 Mbit
Baseband
Twisted pair
100 m max run
1000BASE-T
1000 Mbit/1Gbit
Baseband
Twisted pair
100 m max run
10GBASE-T
10 Gbit
Baseband
Twisted pair
100 m max run
40GBASE-T
40 Gbit
Baseband
Twisted pair
100 m max run
100BASE-FX
100 Mbit
Baseband
Multimode fiber
2 km max run
100BASE-SX
100 Mbit
Baseband
Multimode fiber
1000BASE-SX
1000 Mbit/1Gbit
Baseband
Multimode fiber
500 m max run
1000BASE-LX
1000 Mbit/1 Gbit
Baseband
Single-mode fiber
5 km max run
10GBASE-SR
10 Gbit
Baseband
Multimode fiber
26-400 m max run
10GBASE-LR
10 Gbit
Baseband
Single-mode fiber
10 km max run
CWDM
Coarse wavelength division multiplexing - allows bidirectional communications on a single fiber; supports up to 18 channels
DWDM
Dense wavelength division multiplexing - allows bidirectional communication on a single fiber ; supports more than 200 channels
WDM
Bidirectional wavelength division multiplexing - allows bidirectional communication on a single fiber
Private IP addresses
10.x.x.x
172.16.x.x - 172.31.x.x
192.168.x.x
(RFC 1918)
NAT
Network Address Translation - a gateway router has a single public IP address and every machine on the internal LAN has a private address
PAT
Port Address Translation - having more than one internal machine share a public IP address by using different port numbers (same IP address, different port numbers)
APIPA Address
169.254.x.x
EUI-64
A method in IPv6 whereby a machine can assign itself an interface ID
Multicast
224.0.0.0 to 239.255.255.255
Unicast
A transmission sent to a single address
Anycast
a single IP address is shared between multiple devices (usually servers)
Broadcast
IPv4: the highest available host
Link local
IPv6 address that is used to communicate locally;
FE80::/10
Loopback
IPv4: 127.0.0.1
IPv6: ::1
Default gateway
The private address of the gateway router
VLSM
Variable-length subnet mask: subnetting a subnet
Class A IP address
0-126 /8
Class B IP address
128-191 /16
Class C IP address
192-223 /24
Class D IP address
224-239 (reserved for multicasting)
Class E IP address
240-254 (experimental)
CIDR notation
Classless inter-domain routing
IPv6 Tunneling
Encapsulating IPv6 traffic in an IPv4 packet in order to help transition to IPv6
Dual Stack
Running IPv4 and IPv6 at the same time
Shorthand notation
Eliminate leading zeroes
Can replace a single block of all zeroes with ::
Router Advertisement
IPv6 routers periodically send out availability and configuration messages
SLAAC
Stateless address autoconfiguration - IPv6 analogue to DHCP
Virtual IP
A virtual IP address
Subinterfaces
Dividing a single physical interface into more than one logical interface
FTP
TCP 20 - active transfer of data
TCP 21 - control data
SSH
TCP 22; Secure remote console access
SFTP
TCP 22; Secuire file transfer (uses SSH, so shares port number)
Telnet
TCP 23; Unencrypted remote console access
SMTP
TCP 25; Server-to-server email communication
DNS port
UDP 53; Converts domain names to IP addresses
DHCP ports
UDP 67/68
TFTP
UDP 69; simplified file transfer; no authentication (not generally used in production)
HTTP port
TCP 80
POP3
TCP 110; Receive emails from server
NTP port
UDP 123
IMAP
TCP 143; management of email inbox from multiple clients
SNMP
UDP 161; used to gather statistics from network devices
SNMP Traps sent from UDP 162
LDAP
TCP 389; Lightweight Directory Access Protocol; Stores and retrieves information in a network directory
HTTPS port
TCP 443
SMB
TCP 445; Used by Windows for file sharing, printer sharing, etc.
Syslog
UDP 514; devices send message logs to a central repository (SIEM)
SMTP w/ TLS
TCP 587
LDAPS port
TCP 636
IMAP over SSL
TCP 993
POP3 over SSL
TCP 995
Microsoft SQL server
TCP 1433
Oracle SQLnet
TCP 1521
MySQL port
TCP 3306
RDP
TCP 3389; Windows Remote Desktop Protocol
SIP
TCP 5060/5061; Used to set up/manage VoIP sessions
ICMP
Internet Control Message Protocol - used to send bits of info; works at IP level, no data (ping for example)
TCP
Transport Control Protocol - connection-oriented; 3-way handshake, has methods of sequencing packets in case of out of order delivery
UDP
User Datagram Protocol - low overhead, no connection, unreliable delivery
DHCP Process
Client sends DHCP Discover (UDP 68 to broadcast)
DHCP server sends DHCP Offer to Client (UDP 68 to broadcast)
Client sends DHCP Request to server (UDP to broadcast)
DHCP server sends DHCP Acknowledgement to broadcast
DHCP Scope
IP address range (along with excluded addresses)
DHCP Exclusion Range
The range of addresses that the DHCP server won’t hand out
DHCP Reservation
Specific addresses that are reserved for specific devices
DHCP Dynamic Assignment
Addresses are assigned from a pool of addresses. They are reclaimed after a period of time.
DHCP Static Assignment
Administratively configured addresses (linked to a MAC address)
DHCP Lease Time
How long a device keeps an IP address
DHCP Relay
Sends DHCP messages through a router to other networks (DHCP messages are broadcasts)
DNS
Domain Name System - translates human-readable names to IP addresses.
DNS A / AAAA
Address reccord - defines the IP address of a host
A - IPv4
AAAA - IPv6
DNS CNAME
Canonical name: Provides an alias to a server
Example: “mail”, “chat”, “ftp” can all be set to resolve to “www” in the name records
DNS MX
Mail Exchanger record - contains the name of the mail server - perform additional queries to find IP address
DNS SOA
Start of Authority - describes the DNS zone details (zone name, serial number, refresh/retry/expiry, caching/TTL)
DNS PTR
Pointer - Used for reverse lookups
DNS TXT
Text - human-readable text information (public information)
SPF protocol (sender policy framework)
DKIM (domain keys identified mail)
DNS SRV
Service records - helps to find a specific service (Windows Domain Controller, Instant Messaging, VoIP, etc.)
DNS NS
Lists name servers for a domain
DNS Global Heirarchy
13 Root server clusters
Hundreds of generic TLD (.com, .org, etc.)
Over 275 country code TLD
DNS Zone Transfer
Replicates a DNS database. Changes made on a primary DNS server will be replicated on redundant servers
DNS Authoritative Name Server
The authority for the specific domain. Non-authoritative info is usually from cached info, rather than straight from the server itself
DNS Reverse Lookup
Provide the server with an IP address and it gives you the domain name.
DNS Recursive Lookup
Sends request to DNS server, DNS server does the work and then reports back (server keeps large cache)
DNS Iterative Lookup
Local device does all queries (rather than having a name server do it for you)
Internal DNS
Configured and maintained locally
Contains info on internal devices
External DNS
Managed by third party (Google, etc.)
NTP
Used to keep time synchronized between network devices
NTP Stratum
Describes “distance” from original reference clock
Stratum 0 - Atomic Clock
Stratum 1 - Primary time servers
Stratum 2 - Synced to stratum 1 servers
etc.
NTP Clients
Requests time updates from NTP server
NTP Servers
Responds to time requests from NTP clients
Core (Network architecture)
The “center” of the network, containing Web servers, databases, apps, etc.
Distribution / aggregation layer
Midpoint between core and users, communication between access switches, manages path to end users
Access/Edge layer
Users connect to these switches
Data plane (SDN)
Infrastructure; processing frames/packets, forwarding, trunking, encrypting, NAT, etc.
Control plane (SDN)
Manages actions of data plane; routing tables, session tables, NAT tables, dynamic routing protocols
Management plane (SDN)
Configure/manage the devices
Spine-and-Leaf
Servers connect to leaf switches, which connect to all spine switches. Leafs do not connect to each other. (Top-of-rack switching)
North-South Traffic
In/out to an outside device. Slower, must have tighter security.
East-West Traffic
Traffic between devices in the same data center
FCoE (SAN)
Fibre Channel over Ethernet. No specialized hardware required.
Not routable, runs within a single broadcast domain.
Fibre Channel (SAN)
Specialized high-speed topology to connect servers to storage. Requires a specialized Fibre Channel switch.
Can be used with fiber OR UTP
iSCSI (SAN)
SCSI commands over an IP network. Makes a remote disk look and operate like a local disk.
Public Cloud
Available to everyone on the Internet.
Private Cloud
Your own virtual datacenter
Hybrid Cloud
A combination of public and private clouds
Community Cloud
Several organizations share same goal/requirements (example: a provider that advertises specifically to healthcare)
SaaS
On-demand software; no local installation. GDrive, email, etc. Provider is responsible for security.
IaaS
Hardware as a service; outsourcing equipment. You’re still responsible for the management and security. Ex. Web server providers.
PaaS
Middle ground between IaaS and SaaS. Someone else manages the platform. You supply the code. Provider can supply building blocks.
DaaS
Virtual desktops - applications run on a remote server. Local device is a keyboard, mouse, and screen.
Infrastructure as Code
All hardware can be virtualized and updated in code.
Multitenancy
Many different clients are using the same cloud infrastructure. This brings costs down.
Elasticity
Scale up or down as needed
Scalability (Cloud)