A+ 1001: LAN Flashcards
IP address
4 octets between 0 - 255
Classful address scheme for locations and sublocations: Network portion & Host portion
Network portion
- Class c: 1.1.1.x = 254 hosts
- Class b: 1.1.x.x = 65,534 hosts
- Class a: 1.x.x.x = Millions of hosts
IANA
Internet Assigned Numbers Authority
IP addressing FRAME
Destination MAC Source MAC Destination IP Source IP DATA FCS
IP address with zero on the end
The address for a LAN
IP address with a one on the end
Default gateway, that connects LAN to WAN
Usually a Router
3 things a device needs to connect to the internet
- IP Address
- Subnet Mask
- Default Gateway
How to configure static IP on PC
Network & Sharing Center > Change Adapter settings > Select properties of the network > Select IPv4
Enter IP address, Subnet-mask, and Default gateway
Private IP address
Used on private networks
Class A: 10.x.x.x
Class B: 172.16. - 31x.x
class C: 192.168.x.x
Loopback IP Address
Home or Local Host
127.0.0.1
How to verify that network card is up and running
ping 127.0.0.1
How to find ip address
ipconfig
What is the first thing you should do if the network is down?
Ping the router/default gateway
How to ping continuously?
ping -t [ip]
Old Class addressing for Public IP
Class A: 1.0.0.0 - 126.0.0.0
Class B 128.x.0.0 - 191.x.0.0
Class C: 192.x.x.0 - 223.x.x.0
Class D: 224.x.x.x
Class E 240.x.x.x
class E is reserved
Class D-multicast
224.x.x.x
Used for broadcasting like streaming
NAT
Network address translation
With NAT, internal networks use private IP addresses and share a public address
All gateway routers are NAT enabled by default
Networks that use NAT are invisible to public internet
When a device sends a packet to another device on the WAN the NAT removes the LAN address and inserts its own WAN address, before sending the packet out to the internet. When the packet returns the process is reversed and the packet is forwarded to the LAN device
How to get to your routers web interface?
Enter default gateway IP into the browser
Where does the IP for WAN come from
Assigned by ISP
DHCP
DHCP
Dynamic Host Configuration Protocol
Most Routers have a DHCP server included
Dynamically assigns IP address information to devices on network
Makes it easy for mobile devices to move between networks, like going from home network, to office network, to coffee shop, without having to manually configure ip information
Configure on pc by selecting “Obtain an IP address automatically” from the IPv4 Properties
How to find your DHCP server ip
ipconfig /all
APIPA
Automatic Private IP Addressing
The operating systems fallback in case it cannot find a DHCP server
By default, APIPA will always give 169.254.x.x address. This means that all computers will be on the same network and so can still comunicate with oneanother when DHCP server is down, but wont be able to get onto the internet because the router does not use APIPA
When there is limited connectivity, you can get to other devices in the office, but not the internet, then where should be the first place you look?
check ipconfig to see if you have an APIPA address, if you do then the DHCP server might be down.
Try
- restart network
- ipconfig /renew
What does ipconfig /release do?
Disconnects a device from DHCP server
What does ipconfig /renew do?
Reconnects a device to the DCHP server
How to setup a static or non-APIPA address?
Configure it in the “alternate Configuration” in the IPv4 properties tab
IPv6
128 bit addressing scheme
Eight hex numbers separated by 7 colons
Link-Local Address: Assigned by the device itself, used for local connections
Global unicast address (internet Address): Assigned by the router, used for internet connections
Subnet mask = /64 prefix
Link-local address
IPv6 unicast address
Always starts with Fe80::
Link local addresses allow machines to automatically have an IP address on a network if they haven’t been manually configured or automatically configured by a special server on the network (DHCP).
DNS
Domain Name Server
Port Number
IP address gets you to the right computer.
The Port number gets you to the right application
0 - 65535
Well Known Ports: 0- 1023
Registered Ports: 1024 - 49151
Ephemeral/Dynamic Ports: 49152-65535
Resource Monitor
Windows application that allows monitoring of live networking information
Shows connections on a system
Important Well known and Registered Ports
21 FTP 22 SSH 23 TELNET 25 SMTP 53 DNS 67/68 DHCP 80 HTTP 110 POP3 137-139 NETBIOS/NETBT 143 IMAP 161/162 SNMP 389 LDAP 427 SLP 443 HTTPS 445 SMB/CIFS 548 AFP
Registered Port
3389 RDP
TCP/IP
Transmission Control Protocol / Internet Protocol
Connection-oriented protocol that sends multiple packets of data
Uses 3-way handshake to establish connections
UDP
User datagram protocol
Connectionless protocol and sends multiple packets
ICMP
Connectionless and sends a Single Packet Only (ping command)
PDU
Protocol Data Unit
An organization of packets by protocol
The part of the ethernet frame that a particular protocol is interesting in
- Ethernet Frame
- IP packet
- TCP segment / UDP datagram
IP Packet
A frame that consists out of:
ip (source & destination)
port (source & destination)
data
The ethernet Frame, also includes the source and destination MAC addresses as well as the FCS
TCP segment / UDP datagram
A frame that consists out of only the data and port numbers (source & destination)
DNS
Domain name server
Resolves fully qualified domain names to IP address
DNS is the replacement of the host file, which was what was used prior to DNS to resolve domain names
How does a DNS resolve a domain name?
- Type domain name into browser
- Device contacts DNS server, which has the ip addresses of ROOT servers
- DNS server selects and contacts ROOT Server based on it’s geography
- The Root server will give the DNS server the ip for the appropriate first level server (.com, .org, etc)
- The DNS contacts first level server, the first level server will provide ip for the second level domain server
- The DNS then contacts the second level domain server, which provides the DNS with the ip for the queried domain name. (The DNS server will cache the ip to speed up the next query)
- The DNS server then returns the ip address to the browser
- the browser will cache the ip address for future use
FQDN
Fully Qualified Domain Name
Is a registered domain name
256 character limit
Hierarchy of DNS
Athoritative Servers
- ROOT Servers
- First level domains
- Second Level domains
Non Authoritative
1. DNS Server
Setting up DNS
Automatically provided by DHCP server
To statically configure DNS:
- Network Sharing Center
- Change Adapter Settings
- Select Adapter and click on properties
- Select IPv4 properties
- Set DNS info
IP for public google DNS server
- 8.8.8
8. 8.4.4
How to find your DNS server?
To find DNS run any of the following:
- ipconfig /all
- dnslookup
Records maintained by DNS
A Record: IP address and domain name
MX Record: Mail servers
Cname: Alternate names for an ip address
How do we know that a particular server is not a functioning DNS?
- nslookup
- server [ip of server you want to test]
- any domain name
If it timesout, then it means that the DNS is not functioning
Netbios / netbt
The naming convention designed by windows for lan
provided during setup
A computer will either be part of a work group or an active directory domain
To See or change computer name a group, go to control panel > system
Difference between workgroup and domain
A computer will either be part of a workgroup or an active directory domain
Workgroup:
- most basic type of organization
- no security
- no central admin
- perfect for small networks, where people want to share a printer or files
Domains
- Requires window server system
- Requires setup of Active Directory Domain
- Secure
- Used in Enterprise environment
Homegroup
- More security than workgroup
- no longer used on windows 10
Routers
Filter and forward traffic based on IP addresses
Home and small office routers usually have switches built-in with a WAP (Wireless Access Point)
Enterprise Routers are usually 2 port Routers, with no switch or WAP, these are provided seperately
Routing table
used to direct traffic
Router will look at destination IP on packet and forward the packet to the appropriate port using the Routing Table
WAP
Wireless Access Point
DOCSIS
Cable modem connector
Router Console Port
Serial Port using RS232 language (looks like rj-45)
plugged into a laptop or other device (DB-9 connector) that will be used to program or setup Router
usuall uses putty to interface with the Cysco IOS
How to tell the difference between VGA and DB9 connector
VGA has three rows of 5 pins
DB9 has two rows of 9 pins total
Yost / Rollover cable
RJ-45 serial connector on one end, and DB-9 on the other
SOHO Router
Small office / Home office router
usually has 4 port switch and WAP integrated into router
Common DHCP range
- 168.1.1
192. 168.0.1
Setting up SOHO Router
- Plug into or conncet to device
- The router sends out DHCP range to devices
- Run ipconfig
- If default gateway is APIPA (169.254), then the router is not passing out DHCP. Use the user manual to find out what the routers default ip is and then staticly configure ip
- Access the Router Console in browser by using default gateway ip
- Configure Router
- Wan (dynamic IP)
- LAN (192.268.1.1)
- DHCP (set range)
DHCP Reservation
Reserved addresses that are not passed out during Dynamic Host Configuration
QoS
Quality of Service
Toolset that allows metering of bandwith
UPnP
Universal Plug and Play
When enabled on Router, The router will announce itself to any device within range
LLDP
Link Layer Discovery Protocol
Used by windows to help other devices easily discover it.
Automatically enabled
Can disable it by clicking on adapter properties
SNMP
Simple network management protocol
Tool used for network discovery
VLAN
Virtaul LAN
Turns a switch into 2 or more switches
Used to separate a lan into different or separate networks
Managed Switch
Switch with a user interface
Configuring VLAN on a switch
- plug switch into a router with DHCP so that it will be give an IP
- Go into Router and look at status to find IP of switch
- Access switch UI by entering ip in browser
- Go into VLAN configuration
- Setup new VLAN with selected ports
Network Troubleshooting: No Connectivity
- Check Physical connections (Lan cables, Patch cables) and Power
- Check IP addresses
- Check for IP conflicts
- APIPA (DHCP failure)
- Ping IP addresses
Network troubleshooting: Limited Connectivity
- Check DHCP problems.
- APIPA
- Rouge DHCP (192.168.7.1 instead of 192.168.1.1. )
DHCP server Trace and find the Rouge server
Network Troubleshooting: Intermittent Connectivity
- Problem with cabling interference
- non shielded cabling next to electric devices
Network Troubleshooting: Unavailable Resources
Check if you can get to the system itself (Ping System). IF you can get the system then the problem is likely the shared resource itself, in which case, check the shared resource settings
Network Troubleshooting: Slow connectivity Speed
More a wireless issue
- Check task manager to see how hard network card is being used, and close processes that are using excessive amounts of bandwith
- Take advantage of QOS to prioritize critical tasks
A Class A IP address has how many locked octets?
The first octet of a Class A address, the network address, is locked. The other choices are incorrect.
What does 255 mean in a subnet mask?
The octet is part of the network address
Which is usually true of NAT routers?
a. ) NAT Routers have a private address on the WAN side and a public address on the LAN side
b. ) NAT routers have a private address on the WAN side and a private address on the LAN side
c. ) NAT routers have a public address on the WAN side and a private address on the LAN side
d. ) NAT routers have a public address on the WAN side and a public address on the LAN side
a.) NAT Routers have a private address on the WAN side and a public address on the LAN side
How many bits are in an IPv6 address?
126 Bits
Which service uses port 445?
SMB uses port 445.
What is the maximum number of characters in an FQDN?
255
Fully-qualified domain names can have up to 255 characters, including dots.
