Tuesday, May 22, 2007

Subnetting for Exchange Servers & for FUN




One of the most fun staff Subletting. I have decided to post this question here so that my students can post the answers here. Remember the question, what is an IP address. I have seen some people spending 10 minutes to explain this question. The simple answer would be "It is 32 Bits Binary number. What is a subnet mask than. The answer would be IT is 32 bits binary number as well. Him sound like they are twins, so what does subnet mask do? The answer would be "it divides an IP address into two distinct groups", network portion and host portion. Why is this so important than? Well the answer would be,

IP Address=32Bits Binary number

Subnet mask=32Bits Binary number

IP Address=Network+Host, The subnet Mask determines the Network portion as well as Host portion of the IP Address

If I tell you I live in Washington BLVD and if you live in Washington BLVD, do you think if we are we neighbors? (Assuming Washington Blvd is walkable distance)

Well the answer is maybe or maybe not.

I need my students explain the rest of the story

Here is the question

Given----------- 10.0.0.135/27

User1


  1. What is IP address
  2. What is Subnet mask
  3. What is Default Gateway
  4. What is First Network
  5. What is Default Gateway
  6. What is First Usable IP Address
  7. What is Last Usable IP Address
  8. What is Broadcast IP Address
  9. How many Networks
  10. How many Hosts in each Network


User2 (Located on Network 2th)

  1. What is IP ADDRESS?
  2. What is Subnet Mask?
  3. What is Default Gateway?


Oz Ozugurlu


7 comments:

Oz Ozugurlu said...

Team,
I ask this question often in interviews,
What is /27 subnet mask? You would be surprised to see the answers people are coming up with. I understand and don’t understand being in IT 10 some years and not getting this right?
What is that about?
Best
Oz

Scott said...

/27 = 255.255.255.224 (8networks 30host per network 240 total hosts)

First User
IP Address = 10.0.0.135
Subnet Mask = 255.255.255.224
Default Gateway = 10.0.0.120
5th network.
1st network 10.0.0.1-10.0.0.29
Default Gateway 10.0.0.1
First available 10.0.0.2
Last available 10.0.0.28
Broadcast 10.0.0.29

Second User
8 networks
30 host per network
IP Address = 10.0.0.36
Subnet Mask = 255.255.255.224
Default Gateway = 10.0.0.30

Totally from memory
BEER?

Oz Ozugurlu said...

Himm I will buy you a berr for sure,
I need rest of the class come back here and speak up
Guys am I buying Beer for Scott or not?
Simon?????
Best
oz

Will said...

First User is in the 5th network

IP Address: 10.0.0.135
Subnet Mask: 255.255.255.224
Default Gateway: 10.0.0.121
Network ID: 10.0.0.120
First Network: 10.0.0.0-10.0.0.29
First Usable IP: 10.0.0.122
Last Usable IP: 10.0.0.148
Broadcast IP: 10.0.0.149
Total Networks: 8
Hosts in each Network: 30

User on the 2nd Network

IP address: 10.0.0.35
Subnet Mask: 255.255.255.224
Default Gateway: 10.0.0.1
Network ID: 10.0.0.0

Will said...

User on the 2nd Network

IP address: 10.0.0.35
Subnet Mask: 255.255.255.224
Default Gateway: 10.0.0.31
Network ID: 10.0.0.30

Oz Ozugurlu said...

/27 means 27 Bits Turned on, in total 32 Bits, we have left 5 Bits to play with.

3Bits Network
5Bits for Host

If we do the Math 2*N=Networks, 2*H – 2 = Hosts in each network (why are we minus the number 2 from hosts? Because every network will need a unique IP address to identify the network itself and every network will need a Broadcast IP as well (remember DHCP Process)
2*3=H  8N
2*5-2=H  30H
We used 3Bits which are, 128+64+32=224
Incremental is the smallest Bit which is 32, we will increment this until we go over 255
Network as below ( 0,32,64,96,128,160,192,224,) 256 won’t exist in 8 Bits Binary, max number is all bits (8Bits) turned on, 11111111=255

10.0.0.0 Network1
10.0.0.32 Network2
10.0.0.64 Network3
10.0.0.96 Network4
10.0.0.128 Network5
10.0.0.160 Network6
10.0.0.192 Network7
10.0.0.224 Network8




10.0.0.256------------------------------- Nopeeeeeee 1 above 255, so it won’t work in 8Bits Binary world
In the Example the Given IP is 10.0.0.135 so we expect the see the PC1/USER1 in the same network as this node is. The number 135 fits into the Network .128, because 135 is a number between 128 and 160 networks

This network will be
10.0.0.128 \27 255.255.255.224
10.0.0.129 FGW (respect to a CISCO)
10.0.0.130 FUIP (First usable IP)
10.0.0.158 LUIP (last Usable IP)
10.0.0.159 BIP (Broadcast IP)
10.0.0.160 (Next network)
PC1 IP can be assigned any IP range between 10.0.0.130---------------158

Rodrigo said...

Given: 10.0.0.135/27

Solution to Problem #1:

IP address of network = 10.0.0.128
Subnet mask = 255.255.255.224
Default gateway = 10.0.0.129
1st network = 10.0.0.0
Default gateway of 1st network =
10.0.0.1

1st usable IP address = 10.0.0.130
last usable IP address = 10.0.0.158
Broadcast IP address = 10.0.0.159
Total number of networks = 8
Number of host per network = 30


Solution to Problem #2:

User on 2nd network:

IP address = 10.0.0.32
Subnet mask = 255.255.255.224
Default gateway = 10.0.0.33