LOCAL AREA NETWORKING
- Intro to TCP/IP
- ARPANET formed (basis for Internet)
- TCP/IP adopted as protocol for ARPANET/the Internet
- IP addresses have four octets between 0-255 (a total of 256 options)
- Classful address scheme for locations & sublocations.
- Class A—6.x.x.x
- Only 1st number is locked
- millions of hosts
- Class B—172.16.x.x
- First 2 numbers are locked/set
- 65,534 hosts
- Class C—210.11.12.x
- First 3 numbers are locked/set)
- 254 hosts
- Network IDs and Subnet Masks
- Use Network & Sharing Center for setting up network information
- Set IP address, subnet mask, and gateway in Ethernet Properties
- Manual settings = static IP address
- Private IP Addresses:
- Class A—10.x.x.x
- Class B—172.16.x.x, 172.31.x.x
- Class C—192.168.x.x
- Special IP Addresses
- Class D addresses for multicast (224.x.x.x)
- Class E addresses are reserved (240.x.x.x)
- Three sets of private IP addresses (10, 172.16-172.31, 192.168.x.x)
- Loopback addresses for self-reference (127.x.x.x)
- Loopback IP Address—refers to your own system
- ex: 127.0.0.1
- NAT (Network Address Translation)
- Network Address Translation (NAT) saves IP addresses.
- 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 the public internet
- Dynamic IP Addressing
- Dynamic Host Configuration Protocol (DHCP) automatically assigns IP information to hosts
- Gateway routers commonly are DHCP servers for their internal LANs
- If a DHCP client can’t find the DHCP server, it will use an APIPA address (ex: 169.254.x.x)
- Use the ipconfig/renew command to force a new connection to the DHCP server
- IPv6 (8 groups, of 4 hexadecimal values, separated by 7 colons)
- IPv6 uses a 128-bit addressing scheme
- IPv6 addresses use a hexadecimal notation
- Link local addresses are used for local connections
- Global addresses are used to connect to the internet
- IPv6 addresses can be shortened by removing leading zeros, but be familiar with the rules.
- IPv6 addresses have two IP addresses: a link-local address and an Internet address.
- The second part of the IPv6 address using EUI-64 is generated from the MAC address.
- Port Numbers
- Port numbers get data to the correct application.
- There is always a source and destination port number.
- Servers listen for well-known port numbers (0-1023)
- Resource Monitor shows the connections on a system.
- Memorize all ports numbers listed on the A+ exam.
- Common Port Numbers
- 21–FTP
- 22–SSH
- 23–TELNET
- 25–SMTP
- 53–DNS
- 80–HTTP
- 110–POP3
- 143–IMAP
- 443–HTTPS
- 3389–ROP
- 137-139–NETBIOS/NETBT
- 445–SMB/CIFS
- 427–SLP
- 548–AFP
- TCP, UDP, and ICMP
- Transmission Control Protocol (TCP) is connection-oriented and sends multiple packets.
- User Datagram Protocol (UDP) is connectionless, but also sends multiple packets.
- Internet Control Message Protocol (ICMP) is connectionless and always sends a single packet.
- We organize packets by practical data units (PDUs).
- Understanding DNS
- Domain Name System (DNS) resolves fully-qualified domain names (FQDN) to IP addresses.
- DNS replaced hosts files
- DNS uses a hierarchical organization to resolve FQDNs to IP addresses.
- All Internet-connected hosts have a DNS server.
- Working with DNS
- Use ipconfig /all to see a system’s DNS servers
- You can statically configure DNS and still use DHCP for IP addressing.
- Have an alternative public DNS server in case your DNS server is down
- Use nslookup to verify a DNS server is running
- Working with Workgroups
- Server Message Blocks is the common way Windows file and folder sharing is handled over TCP/IP
- All Windows computers on a single LAN will automatically see each other if they are in the same workgroup.
- You must have an account on a remote system to access shared folders.
- We set share permissions when we share a folder.
- Routers
- Routers filter and forward traffic based on IP addresses
- A routing table determines where to filter or forward IP packets
- Every routing table has a default gateway that sends all data unless otherwise specified.
- A SOHO (Small Office/Home Office) router is usually far more than just a router
- Some routers use web connections, some use console ports.
- The “default gateway” is your router!
- Basic Router Configuration
- Configure both the WAN and the LAN connections on your router.
- Avoid default settings for basic configurations (IP, SSID, password, etc.)
- Don’t create too large of a DHCP pool.
- DHCP reservations set aside IP addresses in the DHCP pool.
- Advanced Router Configuration
- QoS (Quality of Service)
- Link Layer Discovery Protocol (LLDP)
- SNMP (Simple Network Management Protocol)
- QoS gives control on network bandwidth by many different criteria.
- Link Layer Discovery Protocol (LLDP) and Universal Plug and Play (uPnP) help with network device identification.
- Simple Network Management Protocol enables querying of network devices.
- VLANs
- VLANs enable network segmentation without adding hardware.
- Configure VLAN-capable switches via IP addresses & Web browser.
- Use firmware interface for managing VLANs
- Firmware interface also enable features such as port security
- Network Troubleshooting
- Connectivity problems caused by physical or software faults
- External interference can create network problems
- Lack of and/or slow access to resources point to problems as well.
