CST3607 Class Notes 2019-02-14

Assignment #1: Due Tues.

News & Tools


  • The IoT Attack Vector “BlueBorne” Exposes Almost Every Connected Device
  • BlueBorne is an attack vector by which hackers can leverage Bluetooth connections to penetrate and take complete control over targeted devices.
  • BlueBorne affects ordinary computers, mobile phones, and the expanding realm of IoT devices.
  • The attack does not require the targeted device to be paired to the attacker’s device, or even to be set on discoverable mode.

Anti-Virus, or Not?

  • In my opinion, anyone who promotes not using anti-virus and other protective software on all computers and devices that connect to the Internet is being very irresponsible. It is too trivial for systems to be compromised by malware and zero-day exploits.

Using the AND function to determine the network address

  • Use the bitwise AND to determine the network address by comparing the binary of the subnet mask to the binary of an IP address withing the subnet.
    • If both bits in the compared position are 1, the bit in the resulting binary representation is 1, (1 × 1 = 1);
    • Otherwise, the result is 0 (1 × 0 = 0 or 0 × 0 = 0)
    • For example:
      10010010.00101111.10000001.00001011 ( ~ IP Address)
      11111111.11111111.00000000.00000000 ( ~ Subnet Mask)
      10010010.00101111.00000000.00000000 ( ~ Network Address / 1st address in the network/subnet)

Video: Calculate Network, Broadcast and host addresses by ciscoKim

Block Size / Subnet Increment

  • The “interesting octet” in the subnet mask is the last octet where bits are turned on.
  • The block size/subnet increment is determined by subtracting the value of the “interesting octet” of the subnet mask, from 256.
  • The block size is not the number of addresses per subnet.
  • The block size is the increment from one subnet to the next.
PrefixSubnet maskInteresting OctetBlock Size
/26255.255.255.1924th256 – 192 =
/18255.255.192.03rd256 – 192 =
/24255.255.255.03rd256 – 255 =

Broadcast Address

  • Add the Wildcard Mask to the network address to determine the broadcast address
  • Or subtract 1 from the next subnet address to determine the broadcast address of the previous subnet.

Wildcard Mask

Default Mask vs Mask

  • Default Mask is when there is no subnetting or supernetting.

Using the Wildcard mask to determine the last address (a.k.a. broadcast address) within a subnet.

  • For subnetting, the Wildcard mask is the inverse of the subnet mask
  • Each octet of the subnet mask, and its corresponding wildcard mask, must add up to 255.
  • Example:
    • If you have a /26 prefix, the dotted-decimal mask would be:, and then the Wildcard mask would be: (As 192 + 63 = 255 in the 4th octet)

MicroNugget: Wildcard Masks by Keith Barker

Read / Do

Practice makes improvement!

Video: Calculate Network, Broadcast and host addresses by ciscoKim

Assignment #1: Due Tues. Feb. 19, 2019

  • Download the Word document for Assignment #1
  • Determine the Network Address, Subnet Mask (in dotted-decimal notation), Block Size, Wildcard Mask, Broadcast Address
  • Print a hard copy and hand it in at the start of class on Sept. 20.
    • Make sure to print an extra copy for yourself, to review during class.
  • Do not e-mail the completed assignment to me. Hand in the hard copy at the start of class.
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