Enable faster convergence of switch

For port assign to PC, remember to enable portfast so that it will not be involve in the spanning tree re-calculation

configure terminal

interface fast ethernet (port)

spanning-tree portfast

Stop those translating time

If you do not have DNS enable. You can stop those annoying translating time when you accidentally hit enter when typing anything

configure terminal

no ip domain-lookup

Prefix and Subnet

Number of Usable IP addresses

Prefix	Subnet mask	binary form	Total IPs	Usable IPs
/32	255.255.255.255	11111111.11111111.11111111.11111111	XX	XX
/31	255.255.255.254	11111111.11111111.11111111.11111110	2	XX
/30	255.255.255.252	11111111.11111111.11111111.11111100	4	2
/29	255.255.255.248	11111111.11111111.11111111.11111000	8	6
/28	255.255.255.240	11111111.11111111.11111111.11110000	16	14
/27	255.255.255.224	11111111.11111111.11111111.11100000	32	30
/26	255.255.255.192	11111111.11111111.11111111.11000000	64	62
/25	255.255.255.128	11111111.11111111.11111111.10000000	128	126
/24	255.255.255.0	11111111.11111111.11111111.00000000	256	254
/23	255.255.254.0	11111111.11111111.11111110.00000000	512	510
/22	255.255.252.0	11111111.11111111.11111100.00000000	1024	1022
/21	255.255.248.0	11111111.11111111.11111000.00000000	2048	2046
/20	255.255.240.0	11111111.11111111.11110000.00000000	4096	4094
/19	255.255.224.0	11111111.11111111.11100000.00000000	8192	8190

/18 and so on ... ...

***Subnet mask will begin with series of '1' and end with series of  '0', there will not be combination of '1' between '0' and '0' between '1'.

***Total IPs formula 2 to the power of n where n is equal to the number of '1'

***Usable IPs = Total IPs - 2 (2 IPs is due to network and broadcast address)

Switch Password Reset

Press mode button when powered-up

Screen saying password-recovery mechanism started

flash_init

load_helper

dir flash:

rename flash:config.txt flash:config.bak

boot

no to initial configuration dialog

enable

rename flash:config.bak config.txt

copy flash:config.txt system:running-config

copy running-config startup-config

Reset password

Press break or Control-C when powered-up

in ROMMON

confreg 0x2142

reset

no to System Configuration Dialog

enable

configure memory

copy startup-config running-config

exit

configure terminal

configure-register 0x2102

write memory