1. CompTIA Server+ Certification (Exam SK0-004)
2.2 Internet Protocol

2. Configure appropriate settings for an IP host
Describe the properties and characteristics of Internet Protocol (IP) addressing
Configure appropriate settings for an IP host
Troubleshoot IP configuration issues using command-line tools
The number in the bottom right corner of the slides refers back to the page where this topic starts in the course book.
2.2 Internet Protocol

3. The TCP/IP Suite IP (Internet Protocol)
ARP (Address Resolution Protocol)
ICMP (Internet Control Message Protocol)
TCP (Transmission Control Protocol)
UDP (User Datagram Protocol)
Application protocols
2.2 Internet Protocol

4. IPv4 Address Format IP address represents 32-bit binary value
The network number (network ID) - this number is common to all hosts on the same network
The host number (host ID) - this unique number identifies a host on a particular network
32-bit binary value
Expressed in 8-bit octets
        
Converted to dotted decimal notation for entry into configuration dialogs
2.2 Internet Protocol

5. Binary / Decimal Conversion
Number bases
Place value
Base 10 (Decimal)
Base 2 (Binary)
Converting between binary and decimal
2.2 Internet Protocol

6. Subnet Masks IP address represents both a network ID and host ID
A mask is applied to identify the network and host portions
A “1” in the mask means corresponding bit in the address is part of the network ID
“1”s in mask must be contiguous
    – VALID
      INVALID
2.2 Internet Protocol

7. Masking an IP Address (ANDing)
To work out a network ID, given an address and mask in decimal, convert to binary and back
2.2 Internet Protocol

8. Routing Decision
Local network
Remote network
2.2 Internet Protocol

9. IP Class
2.2 Internet Protocol

10. Configuring IP IP Address Subnet Mask Default Gateway
Enter using dotted decimal notation
Subnet Mask
Usually specified in dotted decimal
Default Gateway
IP address of the router handling transmissions to remote networks
Client-side DNS (Domain Name System)
IP address(es) of DNS servers handling name resolution
Client-side WINS (Windows Internet Name Service)
2.2 Internet Protocol

11. DHCP and APIPA Dynamic Host Configuration Protocol
Reduces chance of configuration errors and simplifies administration
Configure IP settings on a central server
Client contacts server to obtain configuration
IP addresses leased from a pool
Critical network infrastructure usually uses static addressing however (to reduce risks from DHCP service failure / compromise)
Automatic IP Addressing (APIPA)
Host that is configured to contact a DHCP server might not be able to
Defaults to using an address from the APIPA range
Can communicate with other APIPA hosts on the local network
2.2 Internet Protocol

12. Public and Private Addressing
Address ranges not routable over the Internet to to to to
Used by hosts for link-local autoconfiguration / Automatic Private IP Addressing (APIPA)
Hosts on the private network must use some mechanism to access the Internet
Network Address Translation (NAT)
Proxy
2.2 Internet Protocol

13. Classless Addressing Classful addressing not sustainable
Classless Interdomain Routing (CIDR)
Netmask does not have to align on an octet boundary
Routing decisions made on basis of network prefix, representing number of bits in mask (e.g. /21)
Some configuration dialogs might require CIDR notation rather than dotted decimal mask (e.g. firewall rule configuration)
2.2 Internet Protocol

14. Planning an IPv4 Addressing Scheme (1)
Consider
Whether you need a public or private addressing scheme
How many networks you need
How many subnetworks you need
How many hosts per subnet
Addressing Rules
Network ID cannot be 127
Network and / or host IDs cannot be all 255 (all 1s in binary)
Network and / or host ID cannot be 0 (all zeros in binary)
Host ID must be unique in the subnet
Network ID must be unique
On the Internet (if using a public addressing scheme)
On your internal system of networks (if using a private addressing scheme)
2.2 Internet Protocol

15. Planning an IPv4 Addressing Scheme (2)
Work out how many subnets are needed
Must be a power of 2
Exponent (the value of “n” in 2n) is the number of bits to add to the default network prefix
Check that subnets allow for sufficient hosts (2n-2 where “n” is number of host bits)
Work out the subnets - deduct the least significant octet in the mask from 256
Work out the next subnet ID - the lowest subnet value higher
Work out the host ranges for each subnet
Take the subnet address and add a binary 1 to it for the first host
Take the next subnet ID and deduct two binary digits from it
2.2 Internet Protocol

16. ipconfig Windows utility reporting IP configuration
ipconfig /all
ipconfig /release AdapterName
ipconfig /renew AdapterName
ipconfig /displaydns
ipconfig /flushdns
Identify static configuration
Look for APIPA address / limited connectivity icon
2.2 Internet Protocol

17. ifconfig Linux utility for reporting and modifying IP configuration
Can be used to change configuration (though changes lost at next boot) and bring adapter up or down
Does not support DHCP or DNS switches
Does not show default gateway (use route)
2.2 Internet Protocol

18. ping ping IPAddress ping HostName
Internet Control Message Protocol (ICMP)
Standard tests
Ping the loopback address (ping )
Ping the host’s IP address
Ping the IP address of the default gateway
Ping the IP address of a remote host
2.2 Internet Protocol

19. Interpreting ping Output
Reply from, round trip time and packet loss
Detect whether a link is slow or experiences packet loss
Use tracert to identify where on the route there is a problem
Destination unreachable
No route to host
Check IP configuration
Check router (default gateway)
No reply / timed out
Host / interface is down
Host cannot route reply
Firewall
2.2 Internet Protocol

20. Troubleshooting Connectivity Issues
Verify configuration (ipconfig / ifconfig)
Check DHCP
Test connectivity with ping
Loopback
Workstation address
Default gateway (or other local host)
2.2 Internet Protocol

21. IP Version 6 IPv4 address shortage IPv6 / IPng Very slow transition!
32-bit address space
Inefficiently allocated
Complex routing tables
IPv6 / IPng
128-bit address space
Cope with mobile / “Internet of Things” growth
Hierarchical address allocation (simpler routing)
Very slow transition!
2.2 Internet Protocol

22. Hexadecimal Numbering
Base 10 (decimal) and place value powers of 10
Base 2 (binary) - 0 or 1 and place value powers of 2
Base 16 (hex) - up to 16 values represented by 0-9 and A, B, C, D, E, F
1 hex digit can represent 4 binary digits (a “nibble”)
2 hex digits can represent 1 octet (byte / 8 bits)
4 hex digits can represent 1 double-byte (16 bits)
2.2 Internet Protocol

23. IPv6 Address Notation 128-bit binary address = lots of typing!
Hex notation
Each hex digit represents 4 binary digits
Hex digits are arranged in 8 x 16-bit (double byte) blocks separated by colons
2001:0db8:0000:0000:0abc:0000:def0:1234
Zero compression
Can omit leading zeroes
Can compress one sequence of “all zero” double bytes
2001:db8::abc:0:def0:1234
2.2 Internet Protocol

24. IPv6 Addressing Schemes
In IPv6, host bits are fixed
Network prefix (64-bit)
Host ID (64-bit)
Global
001 binary prefix (2 or 3 in hex)
Next 45 bits allocated to registries and ISPs
Following 16 bits for subnetting
64 bits for interface
MAC-derived / EUI-64
Pseudo-random token
Link-local
binary prefix (or fe80 in hex)
Not routable
Communicate with same subnet (neighbors)
All interfaces have link-local addresses
2.2 Internet Protocol

25. IPv4 versus IPv6 Misconfiguration
Incorrect address or network prefix
Networks running both IPv4 and IPv6
Which protocol is in use for a given connection
Whether IPv4 or IPv6 are enable or disabled on particular hosts?
2.2 Internet Protocol

26. Configure appropriate settings for an IP host
Describe the properties and characteristics of Internet Protocol (IP) addressing
Configure appropriate settings for an IP host
Troubleshoot IP configuration issues using command-line tools
What is meant by dotted decimal notation? An IP address is a 32-bit number expressed as four octets (bytes). A byte can be expressed as the decimal values and these are used to represent the IP address, with dots between each decimal number. This scheme is easier for people to read than a binary number and reduces configuration errors.
If a host is configured with the subnet mask , what address class could that be related to? Class C. Note that this is an informal designation and does not mean a classful addressing scheme is in place.
A host is configured with the IP address What is significant about this address? It is a private address and cannot be reached directly over the Internet. The host must use a router with address translation or a proxy service to communicate on the Internet.
True or false? The default gateway address is the IP address of a router on a remote network. False - the router must be on the local network for the host to be able to reach it. It is the router's job to send packets on to remote networks.
What is the purpose of a DHCP server? Automatically allocates a TCP/IP configuration (IP address, subnet mask, default gateway, and DNS servers) to hosts when they join the network.
True or false? Classful addressing is a feature of IP version 6. False.
You have restarted the DHCP server following a network problem. What command would you use to refresh the IP configuration on client workstations? ipconfig /renew "Local Area Connection"
What command can you use on a Linux computer to report the IP configuration? ifconfig.
A single server on a network cannot connect to the Internet. Where would you start troubleshooting? You could test the server's IP configuration, specifically the default gateway or name resolution or you could check that the cable is good.
If a host has a firewall configured to block outgoing ICMP traffic, what result would you expect from pinging the host (assuming that the path to the host is otherwise OK)? A failure message (typically "General failure" or "Destination unreachable").
2.2 Internet Protocol

27. Lab 4 / Configuring Network Settings
2.2 Internet Protocol