CCNASUMMARY(转)[@more@]
CCNA study
OSI Model
Application
File, print, message, database, and applications
Determines availability of the target host.
Www, email, ftp, telnet, edi, quake
Presentation
Data Encryption, compression, and translation services
Determines the syntax of the data transfer.
Pict, tiff, jpeg, midi, mpeg, quicktime, etc
Session
Dialog control, coordinates the comunications
Nfs, sql, rpc, x windows, asp (appletalk session protocol), DNA SCP (
digital
whatzit)
Transport
End-to-end communication
Responsible for hiding the communications from the higher layers.
TCP / UDP
Network
Routing
IP / ICMP, BootP, ARP, RARP
Routers
Data Link
Framing
Ethernet II, 802.5 (token ring), 802.3, 802.2 (802.3 with dsap and ssa
p logical
link control fields)
Media access control: MAC: 48 bits, 3 bytes vendor + 3 bytes serial nu
mber
WAN:
High-level datalink control HDLC (cisco default for serial links)
Synchronous Data Link Control SDLC (uses polling)
Link Access Procedure, Balanced LAPB
x.25, slip, ppp, isdn, Frame Relay
Bridges / Switches
Physical
Wire?nbsp;
v.24, v.35, x.21, g.703, hssi, etc
Repeaters / Hubs
DOD Model
Process/application ?nbsp; application, presentation, session
Host-to-host ?nbsp; transport
Internet ?nbsp; network
Network access ?nbsp; Datalink / physical
LAN
Ethernet
802.3 CSMA/CD | Ethernet_II | 802.2
10base2/thinnet: 185 meters
10base5/thicknet: 500 meters
10baseT: can run above 10Mbps 200ish meters
5-4-3 rule: 5 segments, 4 repeaters, 3 segments populated
100BaseTX: 100 meters, up to 2 repeaters. Packets between 512 and
1518.
FDDI
100 Mbps
token passing with dual counter-rotating rings
Token-ring
802.5
4 / 16 Mbps
ATM
53-byte cells
Flow Control
Contention: CSMA/CD : Carrier Sense Multiple Access, Collision
Detect
Token Passing: Token Ring, Fiddi
Polling: SDLC, some HDLC, some HP ethernet stuff
SWITCHING
Store ?nbsp;and ?nbsp;forward
Buffers whole frame before forwarding
Cut-Through
Forward frame as soon as destination address is available
Fragment Free
Does Cut-Through after 64 bytes are received to stop collision packe
ts from
being forwarded.
802.1d Spanning-Tree Protocol STP
detect and eliminates loops in routed network
STA: Spanning Tree Algorithm
Sends out BPDUs: Bridge protocol data units
VLAN:
Virtual Lans
Create 'logical' networks by location, function or department.. Or pro
tocol, or
whatever.
Done with a switch using Frame-Tagging (can be used between switches I
f you
have ISL inter-switch link) Frame-Tagging uses unique user-defined id
entifiers
while within the switch fabric, and is very scalable.
TCP/IP
Port numbers:
TCP: protocol number 6
ftp: 21
telnet: 23
smtp: 25
UDP: protocol number 17
Dns: 53
Tftp: 69
Snmp: 161
TCP Addressing:
0-255: public assigned
256 ?nbsp;1023: assigned to companies
1023+ user defined / source addresses
IP Addressing:
Class leading bits decimal range of first byte
A 0 1-127
B 10 128-191
C 100 192-223
Learn the rest of the stuff? Way out of scope of this.
NOTE:
Cisco considers the mask to be the bits beyond what is 'normal' for th
at class
address, not the entire number of bits in the subnet mask, sometimes?
IPX
Protocl Stack:
1. Application, presentation, session - RIP, SAP, NCP, NLSP, etc?nbsp;
2. Transport - IPX, SPX
3. Network - IPX
4. Data link - ODL Open Data Link
5. Physical - whatever
IPX
Connectionless, and communicates via sockets
Each host runs its own internal ipx network in addition to any lan n
etwork
Addressing:
10 byte address
first 4 bytes are network ?nbsp;need to be unique, otherwise whatever..
Last 6 bytes are node - usually just use the MAC address
SPX
Sequence Packet eXchange
Connection oriented protocol
Creates virtual circuits, with specific connection Ids
RIP
Routing information protocol
Distance vector protocol that establishes routes between ipx network
s
Judges based on ticks (1/18 second units) and hops
Broadcast every 60 seconds
Used to provide each server with a complete network map
SAP
Service advertising protocol
Servers use it to advertise, clients use it to locate services
Broadcast every 60 seconds
NLSP
NetWare Link Services Protocol
Link-state protcol to replace RIP and SAP someday?nbsp;
NCP
NetWare Core Protocol
Provides access to server resources
Netware in a nutshell
1. Strict client-server model (nobody is both)
2. Servers provide files, printing, messaing, applications, and data
bases
3. Every netware server (or cisco router) creates a SAP table of all
services
offered by all servers
4. A client issues a GNS (GetNearestServer request) broadcast to fin
d out
what is on the local SAP
Netware frame types & Features
1.802.3 default on NetWare 3.11
2.802.2 default on NetWare 3.12+
3.ethernet_ii - supports tcp/ip and ipx
4.ethernet_SNAP - appletalk, tcp/ip, and ipx
Routing Protocols
RIP:
Routing Information Protocol
Distance ?nbsp;vector routing protocol
Updates every 30 seconds
Route invalid timer 90 seconds: time before route considered invalid
.
Route flush timer: 240 seconds: route removed from table
Can use metrics (1-15) to weight against some interfaces
15 hop limit
OSPF:
Open Shortest Path First
Link-state routing
Very infrequent broadcast updates
Extremely granular metrics
NLSP:
Novell's Link State Protocol
Link-state
IGRP:
Interior Gateway Routing Protocol (cisco proprietary)
Distance-vector
Metrics and hop count from 1-255
Measures delay in units of 10 milliseconds
Mea
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