what is stp?

STP -spanning tree protocol

• it is used to create loopfree topology
• each cisco switch has its own mac address and bridge id
• bridge id=switch mac address + bridge priority
• bridge id is used to elect main switch or root switch which is then responsible to send updates to neighbours 
• switch with lowest bridge id is called as root bridge
• all ports of root bridge are in forwarding state
• stp allows only single path for each destination
• it blocks multiple path to avoid flooding of data
• stp IS BYDEFAULT ENABLED IN EACH CISCO SWITCH

   

osi layers

 OSI layers

Application layer-it identify user application such as sharing of data,remote connection,internet access etc.

presentation layer-it maintains format of data such as compression,encryption,docx,pptx etc.

session layer-responsible to esablish,maintain and terminate connection between two devices.

transport layer-responsible to transfer data.Functions are flow control,segmentation etc.

segmentation-dividing large size of data into small packets.

source and destination ports are added in this layer

Network layer-responsible to check network connectivity.Also add sr and dest ip addresses to data.

Data link layer-it has two sub layers

1.LLC-logical link control-used to check errors in data

2.MAC-used to add sr and dest mac addresses to data

Physical layer-responsible to check physical connections of devices in network`.

 

types of ip

 Types of IP

1)private ip-

used in LAN

can not access internet using this ip

user can decide about assigning this ip to machines

its not chargable

A-10.0.0.0-10.255.255.255

B-172.16.0.0-172.31.255.255

C-192.168.0.0-192.168.255.255

 These all are private ips

2)public ip-

used in wan or to access internet

ISP provides public ip 

it is chargeble

Ex-9.23.5.8

189.0.0.1

200.34.56.8

subnetting

 172.16.0.0/16

172.16.0.0/20

255.255.11110000.00000000

SM-255.255.240.0

no ip ip=2^12 -2=4094

no of subnets=2^4=16

block size=256-240=16

0,16,32,48.....240

172.16.0.0/20

172.16.0.16/20

172.16.0.32/20

5 ips are reserved by aws---

192.168.20.0/24

192.168.20.0/25

255.255.255.10000000

255.255.255.128

no ip ip=2^7 -2=126

no of subnets=2^1=2

block size=256-128=128

192.168.20.0/25

192.168.20.128/25

what is vpn? short inforamation.

 VPN-virtual private network

-it is used to provide security by encrypting packets

-vpn  uses two types of tunneling protocol

1.GRE-generic routing environment

it only encrypts data not ip addresses

so less secure

2.IPsec-internet protocol security

it encrypts ip and data also 

-it is more secure