Subnetting

 128  64  32  16  8  4  2  1

  0     1    1     0   1  1  0  1 = 111

Determining the number of available valid subnets:

  • How many valid subnets exist on the 10.0.0.0 255.240.0.0 network? 16
  • How many valid subnets are on the 10.0.0.0/12 network? --->prefix notation 16
255.254.0.0 converts to 11111111 11110000 00000000 00000000

Class A 1-126         255.0.0.0                  8 network bits, 24 host bits
Class B 128-191     255.255.0.0              16 network bits, 16 host bits
Class C 192-223     255.255.255.0          24 network bits, 8 host bits

Subnetting is performed by borrowing host bits ONLY. 

Number of valid subnets = (2 to the power of the number of subnet bits)

10.0.0.0 is Class A with 8 network bits. 12-8= 4   2 to the power of 4=16

150.10.0.0 /21   is class B so 21-16= 5   2 to the power of 5 =32

200.1.1.0/27  is class C so 27-24=3 2 to the power of 3 =8

Determining the number of available valid hosts:
(2 to the power of the number of host bits)-2=# of valid host addresses on the subnet

200.10.10.0 /26 is class C so 32-26 =6  2 to the power of the number of 6 = 64   64-2=62 Therefore, there are 62 valid hosts per subnet on 200.10.10.0 /26 

The first address in the subnet is the subnet number itself.
The last address in the subnet is the broadcast address for that subnet. 

Determining the subnet number of an IP Address:

To determine which subnet contains 10.17.2.14/18 follow this simple three-step process:
1. Convert the IP address to a binary string.
2. Add up the network and subnet bits only.

Subnet's broadcast address and range of valid address: 
What is the range of valid IP addresses for the subnet 210.46.111.0 /25? 
210.46.111.1  -  210.46.111.126/25

210.46.444.0            11010010   00101110   01101111   00000000
(Subnet address)
210.46.111.127         11010010  00101110   01101111    01111111
(B' cast address)

Determine the broadcast address and the range of valid IP addresses for the subnet 150.10.64.0 /18

Broad case address is 150.10.127.255

Range of valid address is 150.10.64.1 - 150.10.127.254 /18

Subnetting:

1. Use network 150.50.0.0
2. We need at least 200 subnets.
3. We want 120-150 hosts per subnet. 

Number of valid subnets: 2 to the 9th power = 512
Number of valid hosts: (2 to the 7th power)-2=126
The  winning ask: 255.255.255.128 also expressed as /25.





Comments

Post a Comment

Popular posts from this blog

IP Version 6

 IPv6 address is 128 bits long includes a 64-bit interface identifier and 48-bit prefix and 16-bit subnetting. How many subnets? 2 to the 16th power is 65,536 subnets.  Zero compression: If you have consecutive fields of zeros, they can be expressed with two colons.  1234:1234:0000:0000:0000:0000:32456:3434 1234:1234::3456:3434 Leading zero compression: Leave at least one number in each field, even if the field is all zeros.  1234:0000:1234:0000:1234:0000:1234:01234 1234:0:1234:0:1234:0:1234:123 R2#(config)#ipv6 unicast-routing R2(config)#int gig 0/0 R2(config-if)#ipv6 address 2001:1111:2222:1:2/64 R2#show ipv6 int gig 0/0 Static Routing:  Three types of static routes: Recursive, where only the next-hope address is specified. Directly Connected, where only the output interface is specified. Fully Specified, where both the next-hop address and output interfaces are specified. 
Read more

OSPF

 There are two major link-state protocols in use today - OSPF and IS-IS. IS-IS is primarily used by service providers, and while you'll find IS-IS on other Cisco example, you won't see it on the CCNA R$S exam. So, this will focus on OSPF.  R1#show ip ospf datbase R1#show ip route ospf The beauty of the Dijkstra algorithm is that recalculation of routes due to a network change is so fast that routing loops literally have no time to form.  Before the LSA exchane begins, Ospf-speaking outers must become neighbors by forming an adjacency. Routers must agree on the following to become neighbors in OSPF:  The area number  The hello and dead timer settings Whether the area is a stub area Network mask When you configure RIP, it doesn't require number. However, for EIGRP you need <1-65535> Autonomous system number that has been agreed upon adjacencies. For OSPF, you need <1-65535> Process ID that doesn't have to be agreed upon.  We will verify OSPF adjac...
Read more

Wireless Security

 EAP-MD5 Uses the same MD5 hash as the Cisco router      command : service password-encryption Easily broken EAP-MD% introduced in Win2000, deprecated in Windows Vista LEAP (Lightweight EAP) Cisco-proprietary wireless network authentication method The client and the authentication server challenge each other Challenge responses are encrypted Uses dynamic WEP keys Although officially Cisco proprietary, it's supported by some third-party vendors via the Cisco Compatible Extensions Program LEAP suffers from serious security vulnerabilities, including easily cracked passwords Has been officially deprecated, but is still an option on some clients and access points EAP-FAST (EAP Flexible Authentication by Secure Tunneling) Cisco's replacement for LEAP A secure tunnel between the endpoints is constructed via use of a PAC during a three-phase process, which curiously enough begins with Phase Zero PEAP: Protected EAP Encapsulates EAP via a TLS tunnel The major difference betw...
Read more