CCNA Notes:

Semester 2
2.
Lans and Wans
Wans use serial connections of various types to access bandwidth.
Routers use serial connections to access the WAN
DTE: data terminal equipment (Router)
DCE: data circuit-terminating equipment (Modem)
RAM/DRAM:running config
NVRAM:startup config
Flash: OS image
ROM:Post, bootstrap
Interface: connection for packets to enter/exit the router
LAPD:used for signaling and call setup
PPP, SLIP, Frame Relay are WAN Technologies
T1, E1, xDSL, SONET are dedicated Digital Services
HDLC: High Level Data Link Control Protocol supports PPP and Multiport Configurations
Circuit Switched = POTS, ISDN =
Packet Switched = Dynamic sized cell
Cell Switched = ATM = Static sized cell
Routers use logical address to make decision
4.
CDP = Cisco Discovery Protocol = discovers neighbor routers, starts at boot, performs router discovery
Routers can have up to 5 Telnet Connections
Ping (ICMP) operates at the Transport Layer to test Network Layer Connections
5.
ROM loads bootstrap
Flash locates and loads the OS
NVRAM locates and loads the configuration file or enters "setup" mode (stores the startup config)
RAM (stores the running config)
If no config file is found, the system config dialog/initial configuration mode/setup mode begins
Enable secret word is not required to be the same as enable secret password
If no config file can be found, ROM is searched
6.
7./8.
Cisco IOS Naming Conventions
Hardware Product Platform + Feature Capability + Run Location Compressed Status
NVRAM, Flash, TFTP, Rom = order configs are loaded
show version displays the boot field settings
boot system flash IOS_Filename = tells the router to boot from flash
boot system TFTP IOS_Filename IP = boot from network server
2142 = config register setting during password recovery
2102 = normal register setting
9.
TCP works at the Transport Layer
IP works at the Network Layer
Port numbers are used to keep track of the different conversations the network at the same time
FTP = 21
TELNET = 23
SMTP = 25
DNS = 53
TFTP = 69
SNMP = 161
Exchanging initial sequence numbers during connection sequence ensures recovery later
10.
To map domain names to IPs = identify the host names, name server, and enable DNS
Telnet verifies the application layer software between source and destination. most complete testing mechanism available.
Ping (ICMP) verifies the hardware connection and the logical address at the Internet layer.
Traceroute uses TTL values to test each router along the path.
Extended ping is only in Priv Exec mode
TCP provies flow control by windowing and sequence numbers and acknolodgements.
Ports:
0-255 are for public applications
256-1024 are for marketable applications
1025-65535 are unregulated
11.
Path Determination is a layer three router function.
Routing protocols route routed protocols.
RIP (Routing Internet Protocol
, IGRP, EIGRP, OSPF
OSPF = Link State
RIP = Distance Vector
uses hop counts as metrics
hop count is greater than 15, packet is discarded.
Routing updates broadcast every 30 seconds by default
IGRP = Distance Vector
Versatility enables indefinite, complex topologies
Flexibility uses bandwidth and delay characteristics
Scalable to function in very large networks
90 Broadcast updates
Final.
IGRP must be used with an Autonomous System number
Use Show Version to display the currently running Cisco IOS version
Use Split Horizon to counteract routing loops from incorrect updates
Use Show version to display the boot field setting
If routers have a different set of LSA's, they will disagree about a link.