CCNA -A Short Notes - 3 - IP

Part III – IP

DOD TCP/IP Model:

Layers	OSI Model		Protocols (Port or protocol numbers)	Definition
Process	Application Presentation Session		Telnet (23) FTP (21) TFTP (69) SMTP (25) SNMP (161) DNS (53) BootP NFS DHCP HTTP (80)	Telephone Network - terminal emulation File Transfer Protocol – file transfer that also allows authentication, directory browsing Trivial File Transfer Protocol – stripped down FTP used to backup and restore routers’ config Simple Mail Transfer Protocol – used to send email. POP3 (110) and IMAP (143) retrieve mail Simple Network Management Protocol – collects valuable network info by polling devices (UDP) Domain Name Service – resolves domain names into IP addresses Bootstrap Protocol – used in diskless stations that receive network info and OS from the server Network File System – allows different file system to interoperate. Uses UDP. Dynamic Host Configuration Protocol – enhanced from BootP, can provide IP, subnet, domain, gateway, DNS and WINS information. Uses UDP. Hyper Text Transfer Protocol – WWW protcol
Host-to-Host	Transport		TCP (6) UDP (17) NBP	Transmission Control Protocol – connection-oriented protocol using windowing as flow-control mechanism. Segments are numbered and the number of the last segment received is sent back in the acknowledge message. User Datagram Protocol – unreliable connection-less protocol that has less overhead than TCP. Port numbers: used by TCP and UDP. Numbers 0-1023 are well-known port numbers. Numbers 1024 to 65534 can be used by a transmitting host to initiate the communication. Name Binding Protocol – AppleTalk protocol that matches logical device names to address.
Internet	Network		IP ICMP (1) ARP RARP Routing	Internet Protocol – four-byte number used to route packets on the internet. Connectionless Protocol Internet Control Message Protocol – management protocol and message svc provider for IP. Used in “destination unreachable”, “buffer full”, “hop limit” messages, and in ping and trace. Implemented by all TCP/IP hosts. Address Resolution Protocol – retrieves a MAC address from an IP address Reverse Address Resolution Protocol – retrieves an IP address from a MAC address All routing protocols operate at this layer
Network Access		Data-Link Physical		Ethernet, FastEthernet, Token-Ring, FDDI

                                                                     Data flow in OSI Model

IP Addressing:

Classes:  (n is the network address portion, and h is the host address portion)	Reserved Addresses:
Class A: n.h.h.h, n ∈[0,127] (starts with 0) private: 10/8 Class B: n.n.h.h, n ∈[128.0,191.255] (starts with 10) private: 172.16/12 Class C: n.n.n.h, ∈[192.0.0,223.255.255] (starts with 110) private: 192.168/16 Class D: multicast Class E: research	Network address of 0s : this network or segment Network address of 1s : all networks Host address of 0s : this host Host address of 1s : all hosts Address of 1s : all nodes on current network - flooded broadcast Address of 0s : used by Cisco to designate the default route Address 127.0.0.1 : this node used for loopback tests.

IP Subnetting:

Information	Formula	Mask	Number	Mask	Number
Subnet address	yi=(256-number)*i	10000000	128	11111000	248
First host	yi+1	11000000	192	11111100	252
Last host	yi+1-2	11100000	224	11111110	254
Subnet broadcast address	yi+1-1	11110000	240	11111111	255

i∈ [1,n_s]

Number of subnets: n_s=2^(hostbits-x) – 2 , – hostbits is the number of bits reserved for the host in that class (8 for class C, …)

Number of hosts: n_h=2^x –2

where x is the number of unmasked bits 

It is essential to know how to manipulate subnets to create a given number of hosts or subnets. It is also essential to be able to calculate the broadcast address of a given host or network and subnet mask.