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Network notes.


Partially taken from


Internet Protocol and the Transmission Control Protocol.

IP address is a 32-bit logical number to address a network device. IP are normally represented by decimal numbers, but could be useful sometimes to represent them in binary.

172. 19. 88. 73

An IP address is divided in 4 parts (each 8 bits), these parts are called octets. In the IPV4 there are 5 address classes:

Class A from 1 to 126, in binary the octet start with 0xxx
127 Reserved for loopback, 01111111
Class B from 128 to 191, in binary the octet start with 10xx
Class C from 192 to 223, in binary the octet start with 110x
Class D from 224 to 239, in binary the octet start with 1110 Don’t use. Reserved for the future.
Class E from 240 to 254, in binary the octet start with 1111

IANA reserved 4 address ranges to be used in private networks, these addresses won’t appear on the Internet avoiding IP address conflicts.,, and that means:

– through
– through
– through
– through (reserved for Automatic Private IP Addressing)

The meaning of 8,12 and 16 is

8 =
12 =
16 =

These are subnet mask.

A subnet mask is used to determine which part is the network (n) part and which is the host (H) part.
Default subnet masks:
Class B that is nnnnnnnn.nnnnnnnn.HHHHHHHH.HHHHHHHH
Class C that is nnnnnnnn.nnnnnnnn.nnnnnnnn.HHHHHHHH


Bitwise (logical AND) between IP address and subnet mask to have the IP of the network


To calculate how many subnet in a net mask I can have use the formula (2^n) -2 where n is the number of bits in either field. For example the subnet (11111111.11111111.11110000.00000000 could have (2^4) – 2 = 14 subnets.


Disk Volume Manager notes


Some notes to use Veritas Volume Manager on Solaris

View configuration:

vxprint -th

List disks:
vxdisk list
vxdisk -o alldgs list (shows deported disks)

Replace a failed drive:

vxprint to see which disk is failed. Take note of disk media (dm) and disk group (dg) name.
vxdiskadm to remove (item 4) the failed disk. If there are not hot spare disks answer “none”

Replace phisically the disk.

vxdiskadd to initialize (just initialize) the disk. Say “not” (n) to default disk name, make it as spare disk and to encapsulate it. Don’t set the media disk name but just exit. The new disk is now initialized.

vxdiskadm to substitute the failed/removed disk (option 5).

  • Enter the media disk name.
  • The access name (like c#t#d#s#).

Just some notes to work on cisco equipments


These are just some useful notes to work on Cisco equipments.

The above link is really well written and with lots of information.

If you know almost nothing about network (like me) or if you are sure to know everything about it, it’s better if you take some time to study this field and keep your hands far from switches and routers.

How to set your “terminal emulator program

  • VT100 Emulation
  • 9600 Baud
  • No Parity
  • 8 Data Bits
  • 1 Stop Bit

Enter Privileged Exec Mode

Submit the commad enable (or just ena)

To go back in User Mode disable or just dis.

Set line passwords

  • Console port

Router# configure terminal
Router(config)# line console 0
Router(config-line)# login
Router(config-line)# password your-line-password-here

  • Aux port

Router# configure t
Router# line aux 0
Router(config-line)# login
Router(config-line)# password your-aux-password-here

  • Virtual ports from 0 to 4

Router# configure t
Router# line vty 0 4
Router(config-line)# login
Router(config-line)# password your-vty-password-here

  • “Enable” password

Router# configure t
Router(config)# enable password your-enable-password-here

Show Commands

Router# show interfaces
Router# show startup-config
Router# show conf
Router# show run

Copy, restore and save commands

Router# copy run start
Router# reload

In the next part some useful commands to configure interfaces.

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