IP
address classes
| Class |
Range |
Default
Subnet Mask |
| A |
1-126 |
255.0.0.0 |
| B |
128-191 |
255.255.0.0 |
| C |
192-223 |
255.255.255.0 |
| D |
224 - 239 |
|
|
|
OSI
Reference Model - Layers
| Layer |
Name |
|
| 1 |
Physical |
|
| 2 |
Data Link |
|
| 3 |
Network |
|
| 4 |
Transport |
|
| 5 |
Session |
|
| 6 |
Presentation |
|
| 7 |
Application |
|
|
Switching
types
| Cut-through: |
Reads, processes, and forwards packets as soon as the destination address is looked up and the outgoing port is determined. |
| Store and forward: |
Frames are completely processed before being forwarded out the appropriate port.
|
|
|
| |
Protocols
by OSI layer
OSI Layer Protocols,
services, etc. |
| Physical: |
802.3, 802.5, X.25, FDDI |
| Data Link: |
MAC, LLC, Frame Relay, LAPB, PPP |
| Network: |
IP, ICMP, RIP, IPX, BGP, OSPF, Net BEUI |
| Transport: |
ARP, RARP, TCP, SPX, NBP, UDP |
| Session: |
SCP, SQL, NFS, ZIP, RPC |
| Presentation: |
JPEG, GIF, ASCII, EBCDIC, encryption,
HTML |
| Application: |
Telnet, FTP, SMTP |
|
| |
|
Well-known
ports
| Port Number |
Assignment |
|
| 20/21 |
FTP |
TCP |
| 22 |
SSH |
TCP |
| 23 |
Telnet |
TCP |
| 25 |
SMTP |
TCP |
| 53 |
DNS |
TCP/UDP |
| 69 |
TFTP |
UDP |
| 80 |
HTTP |
TCP |
| 110 |
POP3 |
TCP |
| 119 |
NNTP |
TCP |
| 123 |
NTP |
UDP |
| 161/162 |
SNMP |
TCP |
| 443 |
HTTP over
secure socket
layer |
TCP |
|
|
Steps
of data encapsulation
| 1 |
Application input is converted to data |
| 2 |
Data is converted to segments |
| 3 |
Segments are converted to packets |
| 4 |
Packets are converted into frames |
| 5 |
Frames are converted into bits |
|
Special
and Private IP Addresses
| Class A |
10.0.0.1 – 10.255.255.255 |
| Class B |
172.16.0.0 –
172.31.255.255 |
| Class C |
192.168.0.0 –
192.168.255.255 |
| 0.0.0.0 or
0.0.0.x |
127.0.0.1 (Loop Back) |
| Network
& Host or Host addresses of all 1s: |
| 255.255.255.255
or 192.65.1.255 |
|
|
|
|
|
| LAN
Basics
Hubs direct incoming data packets to all devices connected to the hub.
Hubs can be thought of as a physical extension of the network cabling
media. There are two types of hubs, passive and active. Important
points to remember about hubs: all devices on the hub share
bandwidth; all devices on the hub are in the same collision domain;
and all devices on the hub are in the same broadcast
domain.
Bridges are layer 2 devices (Data Link
layer) which are usually used to segment a LAN into two segments. Bridges examine frames, keeping local traffic local, and forwarding
any non-local traffic. Each port on a bridge is a separate collision
domain. Important points to remember about bridges: each segment
connected to a bridge is in a separate collision domain; all
segments on a bridge are in the same broadcast domain; and bridges forward
all broadcast messages.
Switches are layer 2 devices (Data Link
layer), which operate very similar to bridges, but allow for more
network segments. In fact, switches are often referred to as
multi-port bridges. Each port on a switch provides dedicated
bandwidth. Important points to remember about switches: each segment
connected to a switch is in a separate collision domain, and all
segments on a switch are in the same broadcast domain.
Routers are layer 3 devices (Network
layer), which are used to connect dissimilar LANs and to connect
LANS to WANs (Wide Area Networks). Routers determine a data packets
destination based on the IP destination addresses found in packet
headers, and then routes the packet to its destination using the
best available route. Like bridges and switches, routers create
separate collision domains on each segment connected to the router,
but unlike bridges or switches, routers do not forward broadcast
traffic by default. Important points to
remember about routers: each segment connected to a router is in a
separate collision domain, and each segment on a router is also in a
separate broadcast domain.
LAN segmentation creates more, smaller,
collision domains by creating more segments with fewer hosts on each
segment. Segmentation of a LAN can be accomplished with a bridge,
switch or a router. LAN segmentation does not occur with a hub.
|
| VLAN
Basics
VLAN (Virtual LAN) is a method of logically
segmenting a network by grouping network nodes into different
subnetworks. This is accomplished by assigning a switch port to its
own subgroup of networked nodes. Note that these subgroups are not
limited by physical location. For example, the accounting department
could have rooms on the first, third, and fourth floors of a
building, and also share these same floors with the billing
department. Rather than attempting to physically create networks for
each department or force the departments to always be confined to
certain geographical locations within the building, a
VLAN could be created for each of the departments. VLAN
benefits include increased security and broadcast management. In
a VLAN, broadcasts, as well as any other type of data transmission,
are VLAN specific, meaning that members of VLAN1 will not receive
broadcasts or be able to view any other data intended for members of
VLAN2. VLANs require a router to communicate between
different VLANs. Members of VLAN1 can only communicate with members
of VLAN1. For VLAN1 to communicate with VLAN2, a router is required. VLANs
can be created on a switch by, port address (most
common), MAC address, User ID, and IP address. VLANs can span
multiple switches, but doing so requires that a VLAN trunking
protocol be enabled on each switch port used in a VLAN. VLAN
trunking protocols, such as ISL (Inter-Switch Linking) or IEEE
802.1Q are disabled by default on all ports. |
|
