cvcccccCisco Cisco™ CCNA : OSI and TCP/IP OSI MODEL Application : Responsible for identifying and establishing the avai
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Cisco™ CCNA : OSI and TCP/IP OSI MODEL Application : Responsible for identifying and establishing the availability of desired comm partner and verifying sufficient resources exist for comm. Ex: FTP, SMTP TCP/IP MODEL
Presentation : Responsible for presenting the data in standard formats. Some Presentation layer standards are JPEG, MPEG, MIDI, PICT, Quick Time, TIFF.
Session : Responsible for co-ordinating communication between systems/nodes. Some of the session layer protocols and interfaces: NFS, RPC, SQL, ASP, DNA SCP
Application : Defines TCP/IP application protocols and how host programs interface with transport layer services to use the network. Ex: FTP, SMTP, Telnet
Transport : Provides communication session management between host computers. Ex: TCP, UDP
Transport : Responsible for multiplexing upper-layer applications, session mgmt tearing down of virtual circuits, flow control and to maintain data integrity.
Network : Responsible for sending packets from the source network to the destination network using routing methods. Routers work at network layer.
Datalink : Consists of LLC sublayer and MAC sublayer. LLC handles error control, flow flow control, framing etc. MAC handles access to shared media such as ethernet.
Internet : Performs routing of IP datagrams.
Ex: IP, ARP, ICMP
Physical : Controls the hardware devices and media that make up the network.
Physical : Responsible for ultimate transmission of data over network communications media. Some of the standard interfaces at physical layer are EIA/TIA-232, V.24,V.35, HSSI
Port numbers used by TCP/UDP
Some important port numbers FTP : Port 20-21 TFTP : Port 69
Telnet : Port 23 SMTP : Port 25
DHCP : Ports 67 and 68 DNS : Port 53
POP3 : Port 110 HTTP : Port 80
0-255 : Used for public applications 255-1023 : Assigned to companies Above 1023 : Used by upper layers to set up sessions with other hosts and by TCP to use as source and destination addresses.
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Cisco™ CCNA : IOS Internal memory components of a cisco router
Router Cursor Commands
ROM : Memory containing micro-code for basic functions to start and maintain the router. RAM/DRAM : Stores the running configuration, routing tables, and packet buffers. NVRAM : Memory that does not lose information when power is lost. Stores the system’s configuration file and the configuration register. Flash Memory : Stores the compressed IOS image.
A: Move to the beginning of the command line E: Move to the end of the command line F: Move forward one character, same as using “Right Arrow” B: Move backward one character, same as using “Left Arrow". P: Repeat Previous command, same as using “Up Arrow” N: Repeat Next (more recent) command, same as using "Down Arrow" B: Moves to beginning of previous word. F: Moves to beginning of next word. R: Creates new command prompt, followed by all the characters typed at the last one.
Router Default Boot Sequence for Cisco IOS
Router boot configuration commands
1. NVRAM 2. Flash (sequential)
boot system ROM : boots from system ROM boot system flash : boots IOS from flash memory boot system tftp : boots IOS from a tftp server
3. TFTP server 4. ROM
The router first looks at Startup Config file in NV RAM, if not available, it falls back to Flash, then to TFTP and then to ROM.
Configuration Register Command Router(config)# config-register 0x10x (where that last x is 0-F in hex), when the last