alt.certification.network-plus

Author

Subnet Mask

captain9fingers

2003-08-28, 6:26 am

Hi,

I'm new to this group so hello everyone

I'm studying my network+ at the mo and something I am having difficulty
getting my head round is the "subnet mask" as far as I can tell the reason
there is a subnet mask is so that IP knows whether the address is local or
not.

if I have an IP and subnet mask as follows:

168.168.5.3
255.255.0.0

Does this mean that the computer only tries to resolve the last 2 octets
locally? Does it completely ignore the first 2 octets? If so why?

If your computer has

168.168.5.3
255.255.0.0

and it wants to talk to another computer on the same network

168.168.7.150
255.255.0.0

but also have a conversation with another computer on a different network

168.140.7.150
255.255.0.0

how does it distinguish between the two? The subnet masks are the same but
the 2nd octect of the IP is different but if the computer is only looking at
the last 2 octects would it think the 2 computers are the same?

Hope someone can clear this up for me cos I'm really confused.

Thanks

Chopper

2003-08-28, 8:28 am

"captain9fingers" <spammeasmuchasyouwant@aol.com> wrote in message
news:dmk3b.32$NH4.18@newsfep3-gui.server.ntli.net...
> Hi,
>
> I'm new to this group so hello everyone

>
> I'm studying my network+ at the mo and something I am having difficulty
> getting my head round is the "subnet mask" as far as I can tell the reason
> there is a subnet mask is so that IP knows whether the address is local or
> not.
>
> if I have an IP and subnet mask as follows:
>
> 168.168.5.3
> 255.255.0.0
>
> Does this mean that the computer only tries to resolve the last 2 octets
> locally? Does it completely ignore the first 2 octets? If so why?
>

The subnet mask tells you/the computer which part of the IP address is
network and which is host.
In the example above it tells you that 168.168 is the network address and
5.3 is the host address.
I think resolve is the wrong term as resolving usually applies to finding a
number that applies to a name, eg. www.microsoft.com is resolved to
80.15.236.33. Or in a reverse lookup the name to the number (I say number as
you can resolve to IP, MAC address etc. in different scenarios).
It doesn't ignore the first 2 octets. It uses them to identify the network
and route appropriately.
If you check your routing table (on pc do 'route print' on the command line)
you'll see the Network Destination, Subnet Mask and Gateway.
I hope I'm correct in saying that when your machine wants to reach a remote
machine it will check this routing table and based on the address given it
will route the packet accordingly, eg.
Network Desintation: 168.168.0.0
Netmask(Subnet Mask): 255.255.0.0 (so the first 2 octets are the network
identifier and the second 2 being the host identifier which in this case is
variable as depicted by the 0s)
Gateway: 81.86.210.5 (where to send packets that match the above criteria)
If it does not have an entry that matches the network address then is will
use the default gateway which should take over from there by repeating the
same exercise with it's own routing tables and so on.

I'm still studying for the Network+ exam so if this is wrong, please,
someone correct me so I don't fail!

>
> If your computer has
>
> 168.168.5.3
> 255.255.0.0
>
> and it wants to talk to another computer on the same network
>
> 168.168.7.150
> 255.255.0.0
>
> but also have a conversation with another computer on a different network
>
> 168.140.7.150
> 255.255.0.0
>
> how does it distinguish between the two? The subnet masks are the same but
> the 2nd octect of the IP is different but if the computer is only looking
at
> the last 2 octects would it think the 2 computers are the same?
>
> Hope someone can clear this up for me cos I'm really confused.
>
> Thanks
>
>

FireSword

2003-08-30, 9:29 pm

Ok, The Subnet Mask tells the computer what part of the address you are using as network and what part for hosts.

For example the default Mask for a Class A network like 10.0.0.0 is 255.0.0.0. That implies that only the first octet is used as the network part. However if you need more networks from that address, you can use a subnet mask like 255.255.0.0.
The you can have networks like 10.1.0.0, 10.2.0.0.. etc.

Now, your pc doesn't know in which network it is. so, when it tries to "speak" to other computers it always have to compare the destination IP with the network mask in order to know if the destination PC is on the same network. If it finds that it is on the same LAN then the packet goes directly to the other PC, but if it finds that the destination is not form the same network then your PC sends the packet to the Default Gateway, which is a router that knows how to reach the other network.

The PC uses the binary form of the IP Address,
10.1.1.2 is 00001010.00000001.00000001.0000010
10.1.1.3 is 00001010.00000001.00000001.0000011
10.2.1.2 is 00001010.00000010.00000001.0000010

Let's say PC with IP: 10.1.1.2 , SM: 255.255.0.0 has a packet to send to 10.1.1.3.
The sending PC does a logical AND operation between the destination IP and it's subnet mask:

00001010.00000001.00000001.0000011 (10.1.1.3)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000001.00000000.0000000 (10.1.0.0)

The sending PC knows that the destination IP is on network 10.1.1.0.

Now the sending PC does the same with it's own IP:

00001010.00000001.00000001.0000010 (10.1.1.2)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000001.00000000.0000000 (10.1.0.0)

The sending PC is on network 10.1.0.0 also, so it can send the packet directly to 10.1.1.3. It uses an ARP request to find the MAC Address of the Dest. PC and then creates a frame like this:
Source MAC Address: This PC's MAC Address.
Dest. MAC Address: Destination PC's MAC Address.
Source IP: 10.1.1.2
Dest. IP : 10.2.1.2

Now lets to the same if the PC 10.1.1.2 has to send a packet to 10.2.1.2.

The sending PC does a logical AND operation between the destination IP and it's subnet mask:

00001010.00000010.00000001.0000001 (10.2.1.2)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000010.00000000.0000000 (10.2.0.0)

The sending PC knows that the destination IP is on network 10.2.1.0.

Now the sending PC does the same with it's own IP:

00001010.00000001.00000001.0000010 (10.1.1.2)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000001.00000000.0000000 (10.1.0.0)

Since the destination computer is on a different Network, the PC cannot send the packet directly to the destination, it has to send the packet first to the Default Gateway. Let's say the DG in this case is 10.1.1.1. The sending PC will use an ARP request to find the MAC Address of the DG. Then it will create a packet like this:

Source MAC Address: This PC's MAC Address.
Dest. MAC Address: Default Gateway's MAC Address.
Source IP: 10.1.1.2
Dest. IP : 10.2.1.2

Since the Destination MAC Address is the Router, it will receive the Frame, read the destination IP, look in its routing table and route the packet acordingly.

Keep in mind that the network mask has to be the same on all computers on the network (at least for the scope of Network+) and also that the mask is not always 255 and 0, it can be also 128(10000000), 192(11000000), 224(11100000), 240(11110000), 248(11111000) and 252(11111100).

Hope it helps.
J. Rivera, CCNA, Network+, A+

"captain9fingers" <spammeasmuchasyouwant@aol.com> wrote in message news:dmk3b.32$NH4.18@newsfep3-gui.server.ntli.net...
> Hi,
>
> I'm new to this group so hello everyone

captain9fingers

2003-09-02, 12:32 pm

Thats absolutley brilliant, thanks for providing such a detailed reply

"FireSword" <joxel-spamguard-@hotmail.com> wrote in message news:MPb4b.228$Bc7.198@fe01.atl2.webusenet.com...
Ok, The Subnet Mask tells the computer what part of the address you are using as network and what part for hosts.

For example the default Mask for a Class A network like 10.0.0.0 is 255.0.0.0. That implies that only the first octet is used as the network part. However if you need more networks from that address, you can use a subnet mask like 255.255.0.0.
The you can have networks like 10.1.0.0, 10.2.0.0.. etc.

Now, your pc doesn't know in which network it is. so, when it tries to "speak" to other computers it always have to compare the destination IP with the network mask in order to know if the destination PC is on the same network. If it finds that it is on the same LAN then the packet goes directly to the other PC, but if it finds that the destination is not form the same network then your PC sends the packet to the Default Gateway, which is a router that knows how to reach the other network.

The PC uses the binary form of the IP Address,
10.1.1.2 is 00001010.00000001.00000001.0000010
10.1.1.3 is 00001010.00000001.00000001.0000011
10.2.1.2 is 00001010.00000010.00000001.0000010

Let's say PC with IP: 10.1.1.2 , SM: 255.255.0.0 has a packet to send to 10.1.1.3.
The sending PC does a logical AND operation between the destination IP and it's subnet mask:

00001010.00000001.00000001.0000011 (10.1.1.3)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000001.00000000.0000000 (10.1.0.0)

The sending PC knows that the destination IP is on network 10.1.1.0.

Now the sending PC does the same with it's own IP:

00001010.00000001.00000001.0000010 (10.1.1.2)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000001.00000000.0000000 (10.1.0.0)

The sending PC is on network 10.1.0.0 also, so it can send the packet directly to 10.1.1.3. It uses an ARP request to find the MAC Address of the Dest. PC and then creates a frame like this:
Source MAC Address: This PC's MAC Address.
Dest. MAC Address: Destination PC's MAC Address.
Source IP: 10.1.1.2
Dest. IP : 10.2.1.2

Now lets to the same if the PC 10.1.1.2 has to send a packet to 10.2.1.2.

The sending PC does a logical AND operation between the destination IP and it's subnet mask:

00001010.00000010.00000001.0000001 (10.2.1.2)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000010.00000000.0000000 (10.2.0.0)

The sending PC knows that the destination IP is on network 10.2.1.0.

Now the sending PC does the same with it's own IP:

00001010.00000001.00000001.0000010 (10.1.1.2)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000001.00000000.0000000 (10.1.0.0)

Since the destination computer is on a different Network, the PC cannot send the packet directly to the destination, it has to send the packet first to the Default Gateway. Let's say the DG in this case is 10.1.1.1. The sending PC will use an ARP request to find the MAC Address of the DG. Then it will create a packet like this:

Source MAC Address: This PC's MAC Address.
Dest. MAC Address: Default Gateway's MAC Address.
Source IP: 10.1.1.2
Dest. IP : 10.2.1.2

Since the Destination MAC Address is the Router, it will receive the Frame, read the destination IP, look in its routing table and route the packet acordingly.

Keep in mind that the network mask has to be the same on all computers on the network (at least for the scope of Network+) and also that the mask is not always 255 and 0, it can be also 128(10000000), 192(11000000), 224(11100000), 240(11110000), 248(11111000) and 252(11111100).

Hope it helps.
J. Rivera, CCNA, Network+, A+

"captain9fingers" <spammeasmuchasyouwant@aol.com> wrote in message news:dmk3b.32$NH4.18@newsfep3-gui.server.ntli.net...
> Hi,
>
> I'm new to this group so hello everyone

DaveL

2003-09-22, 5:25 pm

Very nice. If I have a subnet mask of 255.255.254.0. Does that essentially
double the number of locals hosts I can have?

Dave
A+

"FireSword" <joxel-spamguard-@hotmail.com> wrote in message
news:MPb4b.228$Bc7.198@fe01.atl2.webusenet.com...
Ok, The Subnet Mask tells the computer what part of the address you are
using as network and what part for hosts.

For example the default Mask for a Class A network like 10.0.0.0 is
255.0.0.0. That implies that only the first octet is used as the network
part. However if you need more networks from that address, you can use a
subnet mask like 255.255.0.0.
The you can have networks like 10.1.0.0, 10.2.0.0.. etc.

Now, your pc doesn't know in which network it is. so, when it tries to
"speak" to other computers it always have to compare the destination IP with
the network mask in order to know if the destination PC is on the same
network. If it finds that it is on the same LAN then the packet goes
directly to the other PC, but if it finds that the destination is not form
the same network then your PC sends the packet to the Default Gateway, which
is a router that knows how to reach the other network.

The PC uses the binary form of the IP Address,
10.1.1.2 is 00001010.00000001.00000001.0000010
10.1.1.3 is 00001010.00000001.00000001.0000011
10.2.1.2 is 00001010.00000010.00000001.0000010

Let's say PC with IP: 10.1.1.2 , SM: 255.255.0.0 has a packet to send to
10.1.1.3.
The sending PC does a logical AND operation between the destination IP and
it's subnet mask:

00001010.00000001.00000001.0000011 (10.1.1.3)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000001.00000000.0000000 (10.1.0.0)

The sending PC knows that the destination IP is on network 10.1.1.0.

Now the sending PC does the same with it's own IP:

00001010.00000001.00000001.0000010 (10.1.1.2)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000001.00000000.0000000 (10.1.0.0)

The sending PC is on network 10.1.0.0 also, so it can send the packet
directly to 10.1.1.3. It uses an ARP request to find the MAC Address of the
Dest. PC and then creates a frame like this:
Source MAC Address: This PC's MAC Address.
Dest. MAC Address: Destination PC's MAC Address.
Source IP: 10.1.1.2
Dest. IP : 10.2.1.2

Now lets to the same if the PC 10.1.1.2 has to send a packet to 10.2.1.2.

The sending PC does a logical AND operation between the destination IP and
it's subnet mask:

00001010.00000010.00000001.0000001 (10.2.1.2)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000010.00000000.0000000 (10.2.0.0)

The sending PC knows that the destination IP is on network 10.2.1.0.

Now the sending PC does the same with it's own IP:

00001010.00000001.00000001.0000010 (10.1.1.2)
11111111.11111111.00000000.0000000 (255.255.0.0)
--------------------------------------------
00001010.00000001.00000000.0000000 (10.1.0.0)

Since the destination computer is on a different Network, the PC cannot send
the packet directly to the destination, it has to send the packet first to
the Default Gateway. Let's say the DG in this case is 10.1.1.1. The sending
PC will use an ARP request to find the MAC Address of the DG. Then it will
create a packet like this:

Source MAC Address: This PC's MAC Address.
Dest. MAC Address: Default Gateway's MAC Address.
Source IP: 10.1.1.2
Dest. IP : 10.2.1.2

Since the Destination MAC Address is the Router, it will receive the Frame,
read the destination IP, look in its routing table and route the packet
acordingly.

Keep in mind that the network mask has to be the same on all computers on
the network (at least for the scope of Network+) and also that the mask is
not always 255 and 0, it can be also 128(10000000), 192(11000000),
224(11100000), 240(11110000), 248(11111000) and 252(11111100).

Hope it helps.
J. Rivera, CCNA, Network+, A+

"captain9fingers" <spammeasmuchasyouwant@aol.com> wrote in message
news:dmk3b.32$NH4.18@newsfep3-gui.server.ntli.net...
> Hi,
>
> I'm new to this group so hello everyone

FireSword

2003-09-22, 8:25 pm

Not in the example I gave..

If you have a Class A Network with the mask 255.255.0.0 you can have 254
Subnets, each with 65,534 hosts.
if you change the mask to 255.255.254.0 now you have 32,768 subnets with 510
hosts on each subnet.

Also, remember that the number of subnets and hosts always depend on the
network Class you are using.
For a Class C Network you can't use a mask shorter than 255.255.255.0. So
you have to borrow bits from the last octet to create the subnets you need.
If you use 3 bits for subnetting and 5 for hosts, your mask is
255.255.255.224, you have (2^3)-2 = 6 subnets and (2^5)-2=32 valid hosts.
In this case the IP 192.168.1.68 and the IP 192.168.1.132 would be in
different subnets.

On Cisco equipment however you can use the first and last subnet also if you
want, the formula for subnets is then 2^3 = 8.

"DaveL" <dave1027@comcast.net> wrote in message
news:6bSdnTpgYes0_vKiU-KYvA@comcast.com...
> Very nice. If I have a subnet mask of 255.255.254.0. Does that
essentially
> double the number of locals hosts I can have?
>
> Dave
> A+
>
>
>
> "FireSword" <joxel-spamguard-@hotmail.com> wrote in message
> news:MPb4b.228$Bc7.198@fe01.atl2.webusenet.com...
> Ok, The Subnet Mask tells the computer what part of the address you are
> using as network and what part for hosts.
>
> For example the default Mask for a Class A network like 10.0.0.0 is
> 255.0.0.0. That implies that only the first octet is used as the network
> part. However if you need more networks from that address, you can use a
> subnet mask like 255.255.0.0.
> The you can have networks like 10.1.0.0, 10.2.0.0.. etc.
>
> Now, your pc doesn't know in which network it is. so, when it tries to
> "speak" to other computers it always have to compare the destination IP
with
> the network mask in order to know if the destination PC is on the same
> network. If it finds that it is on the same LAN then the packet goes
> directly to the other PC, but if it finds that the destination is not form
> the same network then your PC sends the packet to the Default Gateway,
which
> is a router that knows how to reach the other network.
>
> The PC uses the binary form of the IP Address,
> 10.1.1.2 is 00001010.00000001.00000001.0000010
> 10.1.1.3 is 00001010.00000001.00000001.0000011
> 10.2.1.2 is 00001010.00000010.00000001.0000010
>
> Let's say PC with IP: 10.1.1.2 , SM: 255.255.0.0 has a packet to send to
> 10.1.1.3.
> The sending PC does a logical AND operation between the destination IP and
> it's subnet mask:
>
> 00001010.00000001.00000001.0000011 (10.1.1.3)
> 11111111.11111111.00000000.0000000 (255.255.0.0)
> --------------------------------------------
> 00001010.00000001.00000000.0000000 (10.1.0.0)
>
> The sending PC knows that the destination IP is on network 10.1.1.0.
>
> Now the sending PC does the same with it's own IP:
>
> 00001010.00000001.00000001.0000010 (10.1.1.2)
> 11111111.11111111.00000000.0000000 (255.255.0.0)
> --------------------------------------------
> 00001010.00000001.00000000.0000000 (10.1.0.0)
>
> The sending PC is on network 10.1.0.0 also, so it can send the packet
> directly to 10.1.1.3. It uses an ARP request to find the MAC Address of
the
> Dest. PC and then creates a frame like this:
> Source MAC Address: This PC's MAC Address.
> Dest. MAC Address: Destination PC's MAC Address.
> Source IP: 10.1.1.2
> Dest. IP : 10.2.1.2
>
>
> Now lets to the same if the PC 10.1.1.2 has to send a packet to 10.2.1.2.
>
> The sending PC does a logical AND operation between the destination IP and
> it's subnet mask:
>
> 00001010.00000010.00000001.0000001 (10.2.1.2)
> 11111111.11111111.00000000.0000000 (255.255.0.0)
> --------------------------------------------
> 00001010.00000010.00000000.0000000 (10.2.0.0)
>
> The sending PC knows that the destination IP is on network 10.2.1.0.
>
> Now the sending PC does the same with it's own IP:
>
> 00001010.00000001.00000001.0000010 (10.1.1.2)
> 11111111.11111111.00000000.0000000 (255.255.0.0)
> --------------------------------------------
> 00001010.00000001.00000000.0000000 (10.1.0.0)
>
> Since the destination computer is on a different Network, the PC cannot
send
> the packet directly to the destination, it has to send the packet first to
> the Default Gateway. Let's say the DG in this case is 10.1.1.1. The
sending
> PC will use an ARP request to find the MAC Address of the DG. Then it will
> create a packet like this:
>
> Source MAC Address: This PC's MAC Address.
> Dest. MAC Address: Default Gateway's MAC Address.
> Source IP: 10.1.1.2
> Dest. IP : 10.2.1.2
>
> Since the Destination MAC Address is the Router, it will receive the
Frame,
> read the destination IP, look in its routing table and route the packet
> acordingly.
>
> Keep in mind that the network mask has to be the same on all computers on
> the network (at least for the scope of Network+) and also that the mask is
> not always 255 and 0, it can be also 128(10000000), 192(11000000),
> 224(11100000), 240(11110000), 248(11111000) and 252(11111100).
>
> Hope it helps.
> J. Rivera, CCNA, Network+, A+
>
>
> "captain9fingers" <spammeasmuchasyouwant@aol.com> wrote in message
> news:dmk3b.32$NH4.18@newsfep3-gui.server.ntli.net...
> > Hi,
> >
> > I'm new to this group so hello everyone

> >
> > I'm studying my network+ at the mo and something I am having difficulty
> > getting my head round is the "subnet mask" as far as I can tell the
reason
> > there is a subnet mask is so that IP knows whether the address is local
or
> > not.
> >
> > if I have an IP and subnet mask as follows:
> >
> > 168.168.5.3
> > 255.255.0.0
> >
> > Does this mean that the computer only tries to resolve the last 2 octets
> > locally? Does it completely ignore the first 2 octets? If so why?
> >
> >
> >
> > If your computer has
> >
> > 168.168.5.3
> > 255.255.0.0
> >
> > and it wants to talk to another computer on the same network
> >
> > 168.168.7.150
> > 255.255.0.0
> >
> > but also have a conversation with another computer on a different
network
> >
> > 168.140.7.150
> > 255.255.0.0
> >
> > how does it distinguish between the two? The subnet masks are the same
but
> > the 2nd octect of the IP is different but if the computer is only
looking
> at
> > the last 2 octects would it think the 2 computers are the same?
> >
> > Hope someone can clear this up for me cos I'm really confused.
> >
> > Thanks
> >
> >
>
>

DaveL

2003-09-23, 4:27 pm

Thank's you are a wealth of knowledge.

I was wondering if you can answer an unrelated question.

If I have a raid5 with three drives and I'm running out of space, can I add
drives and run Partition magic to expand the raid to include the added
drives without having to back up, reinitialize the raid and restore?

Dave

"FireSword" <joxel-spamguard-@hotmail.com> wrote in message
news:YYLbb.218$Fq.50@fe05.atl2.webusenet.com...
> Not in the example I gave..
>
> If you have a Class A Network with the mask 255.255.0.0 you can have 254
> Subnets, each with 65,534 hosts.
> if you change the mask to 255.255.254.0 now you have 32,768 subnets with
510
> hosts on each subnet.
>
> Also, remember that the number of subnets and hosts always depend on the
> network Class you are using.
> For a Class C Network you can't use a mask shorter than 255.255.255.0. So
> you have to borrow bits from the last octet to create the subnets you
need.
> If you use 3 bits for subnetting and 5 for hosts, your mask is
> 255.255.255.224, you have (2^3)-2 = 6 subnets and (2^5)-2=32 valid hosts.
> In this case the IP 192.168.1.68 and the IP 192.168.1.132 would be in
> different subnets.
>
> On Cisco equipment however you can use the first and last subnet also if
you
> want, the formula for subnets is then 2^3 = 8.
>
>
> "DaveL" <dave1027@comcast.net> wrote in message
> news:6bSdnTpgYes0_vKiU-KYvA@comcast.com...
> > Very nice. If I have a subnet mask of 255.255.254.0. Does that
> essentially
> > double the number of locals hosts I can have?
> >
> > Dave
> > A+
> >
> >
> >
> > "FireSword" <joxel-spamguard-@hotmail.com> wrote in message
> > news:MPb4b.228$Bc7.198@fe01.atl2.webusenet.com...
> > Ok, The Subnet Mask tells the computer what part of the address you are
> > using as network and what part for hosts.
> >
> > For example the default Mask for a Class A network like 10.0.0.0 is
> > 255.0.0.0. That implies that only the first octet is used as the network
> > part. However if you need more networks from that address, you can use a
> > subnet mask like 255.255.0.0.
> > The you can have networks like 10.1.0.0, 10.2.0.0.. etc.
> >
> > Now, your pc doesn't know in which network it is. so, when it tries to
> > "speak" to other computers it always have to compare the destination IP
> with
> > the network mask in order to know if the destination PC is on the same
> > network. If it finds that it is on the same LAN then the packet goes
> > directly to the other PC, but if it finds that the destination is not
form
> > the same network then your PC sends the packet to the Default Gateway,
> which
> > is a router that knows how to reach the other network.
> >
> > The PC uses the binary form of the IP Address,
> > 10.1.1.2 is 00001010.00000001.00000001.0000010
> > 10.1.1.3 is 00001010.00000001.00000001.0000011
> > 10.2.1.2 is 00001010.00000010.00000001.0000010
> >
> > Let's say PC with IP: 10.1.1.2 , SM: 255.255.0.0 has a packet to send to
> > 10.1.1.3.
> > The sending PC does a logical AND operation between the destination IP
and
> > it's subnet mask:
> >
> > 00001010.00000001.00000001.0000011 (10.1.1.3)
> > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > --------------------------------------------
> > 00001010.00000001.00000000.0000000 (10.1.0.0)
> >
> > The sending PC knows that the destination IP is on network 10.1.1.0.
> >
> > Now the sending PC does the same with it's own IP:
> >
> > 00001010.00000001.00000001.0000010 (10.1.1.2)
> > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > --------------------------------------------
> > 00001010.00000001.00000000.0000000 (10.1.0.0)
> >
> > The sending PC is on network 10.1.0.0 also, so it can send the packet
> > directly to 10.1.1.3. It uses an ARP request to find the MAC Address of
> the
> > Dest. PC and then creates a frame like this:
> > Source MAC Address: This PC's MAC Address.
> > Dest. MAC Address: Destination PC's MAC Address.
> > Source IP: 10.1.1.2
> > Dest. IP : 10.2.1.2
> >
> >
> > Now lets to the same if the PC 10.1.1.2 has to send a packet to
10.2.1.2.
> >
> > The sending PC does a logical AND operation between the destination IP
and
> > it's subnet mask:
> >
> > 00001010.00000010.00000001.0000001 (10.2.1.2)
> > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > --------------------------------------------
> > 00001010.00000010.00000000.0000000 (10.2.0.0)
> >
> > The sending PC knows that the destination IP is on network 10.2.1.0.
> >
> > Now the sending PC does the same with it's own IP:
> >
> > 00001010.00000001.00000001.0000010 (10.1.1.2)
> > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > --------------------------------------------
> > 00001010.00000001.00000000.0000000 (10.1.0.0)
> >
> > Since the destination computer is on a different Network, the PC cannot
> send
> > the packet directly to the destination, it has to send the packet first
to
> > the Default Gateway. Let's say the DG in this case is 10.1.1.1. The
> sending
> > PC will use an ARP request to find the MAC Address of the DG. Then it
will
> > create a packet like this:
> >
> > Source MAC Address: This PC's MAC Address.
> > Dest. MAC Address: Default Gateway's MAC Address.
> > Source IP: 10.1.1.2
> > Dest. IP : 10.2.1.2
> >
> > Since the Destination MAC Address is the Router, it will receive the
> Frame,
> > read the destination IP, look in its routing table and route the packet
> > acordingly.
> >
> > Keep in mind that the network mask has to be the same on all computers
on
> > the network (at least for the scope of Network+) and also that the mask
is
> > not always 255 and 0, it can be also 128(10000000), 192(11000000),
> > 224(11100000), 240(11110000), 248(11111000) and 252(11111100).
> >
> > Hope it helps.
> > J. Rivera, CCNA, Network+, A+
> >
> >
> > "captain9fingers" <spammeasmuchasyouwant@aol.com> wrote in message
> > news:dmk3b.32$NH4.18@newsfep3-gui.server.ntli.net...
> > > Hi,
> > >
> > > I'm new to this group so hello everyone

> > >
> > > I'm studying my network+ at the mo and something I am having
difficulty
> > > getting my head round is the "subnet mask" as far as I can tell the
> reason
> > > there is a subnet mask is so that IP knows whether the address is
local
> or

> > > not.
> > >
> > > if I have an IP and subnet mask as follows:
> > >
> > > 168.168.5.3
> > > 255.255.0.0
> > >
> > > Does this mean that the computer only tries to resolve the last 2
octets
> > > locally? Does it completely ignore the first 2 octets? If so why?
> > >
> > >
> > >
> > > If your computer has
> > >
> > > 168.168.5.3
> > > 255.255.0.0
> > >
> > > and it wants to talk to another computer on the same network
> > >
> > > 168.168.7.150
> > > 255.255.0.0
> > >
> > > but also have a conversation with another computer on a different
> network
> > >
> > > 168.140.7.150
> > > 255.255.0.0
> > >
> > > how does it distinguish between the two? The subnet masks are the same
> but
> > > the 2nd octect of the IP is different but if the computer is only
> looking
> > at
> > > the last 2 octects would it think the 2 computers are the same?
> > >
> > > Hope someone can clear this up for me cos I'm really confused.
> > >
> > > Thanks
> > >
> > >
> >
> >
>
>
>

FireSword

2003-09-24, 7:25 pm

Sorry, not with Partition Magic.
The RAID Controller is where you change your set-up.
Different Controllers let you do different things, however I don't think you
can just add disks to a RAID 5.
When you write a block of data in a RAID 5, half of the block goes to the
first disk, the other half to the second disk, and the Error Correction Code
goes to the third disk. Now, in the next block of data you start in the
second disk, so the ECC goes to the first disk and so on.
Adding a disk means that all of the data and error correction needs to be
re-distributed again.

You do have this option:
Buy 3 larger disks.
Replace the first disk only and wait for the system to rebuild the data on
that disk.
Then Replace the Second and do the same, then the third.

You will end up with the same amount of space in your volume, but now it is
possible that your controller will let you expand the Logical
Drive(partition).

If it doesn't, you can use the extra space to create another logical Drive,
which you can add to the current Volume under the same Drive Letter.
Hope this helps!
J.

"DaveL" <dave1027@comcast.net> wrote in message
news:xIqcnf01_viAPe2iU-KYhA@comcast.com...
> Thank's you are a wealth of knowledge.
>
> I was wondering if you can answer an unrelated question.
>
> If I have a raid5 with three drives and I'm running out of space, can I
add
> drives and run Partition magic to expand the raid to include the added
> drives without having to back up, reinitialize the raid and restore?
>
> Dave
>
>
> "FireSword" <joxel-spamguard-@hotmail.com> wrote in message
> news:YYLbb.218$Fq.50@fe05.atl2.webusenet.com...
> > Not in the example I gave..
> >
> > If you have a Class A Network with the mask 255.255.0.0 you can have 254
> > Subnets, each with 65,534 hosts.
> > if you change the mask to 255.255.254.0 now you have 32,768 subnets with
> 510
> > hosts on each subnet.
> >
> > Also, remember that the number of subnets and hosts always depend on the
> > network Class you are using.
> > For a Class C Network you can't use a mask shorter than 255.255.255.0.
So
> > you have to borrow bits from the last octet to create the subnets you
> need.
> > If you use 3 bits for subnetting and 5 for hosts, your mask is
> > 255.255.255.224, you have (2^3)-2 = 6 subnets and (2^5)-2=32 valid
hosts.
> > In this case the IP 192.168.1.68 and the IP 192.168.1.132 would be in
> > different subnets.
> >
> > On Cisco equipment however you can use the first and last subnet also if
> you
> > want, the formula for subnets is then 2^3 = 8.
> >
> >
> > "DaveL" <dave1027@comcast.net> wrote in message
> > news:6bSdnTpgYes0_vKiU-KYvA@comcast.com...
> > > Very nice. If I have a subnet mask of 255.255.254.0. Does that
> > essentially
> > > double the number of locals hosts I can have?
> > >
> > > Dave
> > > A+
> > >
> > >
> > >
> > > "FireSword" <joxel-spamguard-@hotmail.com> wrote in message
> > > news:MPb4b.228$Bc7.198@fe01.atl2.webusenet.com...
> > > Ok, The Subnet Mask tells the computer what part of the address you
are[c
olor=darkred]
> > > using as network and what part for hosts.
> > >
> > > For example the default Mask for a Class A network like 10.0.0.0 is
> > > 255.0.0.0. That implies that only the first octet is used as the[/color]
network
> > > part. However if you need more networks from that address, you can use
a[col
or=darkred]
> > > subnet mask like 255.255.0.0.
> > > The you can have networks like 10.1.0.0, 10.2.0.0.. etc.
> > >
> > > Now, your pc doesn't know in which network it is. so, when it tries to
> > > "speak" to other computers it always have to compare the destination[/color]
IP
> > with
> > > the network mask in order to know if the destination PC is on the same
> > > network. If it finds that it is on the same LAN then the packet goes
> > > directly to the other PC, but if it finds that the destination is not
> form
> > > the same network then your PC sends the packet to the Default Gateway,
> > which
> > > is a router that knows how to reach the other network.
> > >
> > > The PC uses the binary form of the IP Address,
> > > 10.1.1.2 is 00001010.00000001.00000001.0000010
> > > 10.1.1.3 is 00001010.00000001.00000001.0000011
> > > 10.2.1.2 is 00001010.00000010.00000001.0000010
> > >
> > > Let's say PC with IP: 10.1.1.2 , SM: 255.255.0.0 has a packet to send
to[co
lor=darkred]
> > > 10.1.1.3.
> > > The sending PC does a logical AND operation between the destination IP
> and
> > > it's subnet mask:
> > >
> > > 00001010.00000001.00000001.0000011 (10.1.1.3)
> > > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > > --------------------------------------------
> > > 00001010.00000001.00000000.0000000 (10.1.0.0)
> > >
> > > The sending PC knows that the destination IP is on network 10.1.1.0.
> > >
> > > Now the sending PC does the same with it's own IP:
> > >
> > > 00001010.00000001.00000001.0000010 (10.1.1.2)
> > > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > > --------------------------------------------
> > > 00001010.00000001.00000000.0000000 (10.1.0.0)
> > >
> > > The sending PC is on network 10.1.0.0 also, so it can send the packet
> > > directly to 10.1.1.3. It uses an ARP request to find the MAC Address[/color]
of
> > the
> > > Dest. PC and then creates a frame like this:
> > > Source MAC Address: This PC's MAC Address.
> > > Dest. MAC Address: Destination PC's MAC Address.
> > > Source IP: 10.1.1.2
> > > Dest. IP : 10.2.1.2
> > >
> > >
> > > Now lets to the same if the PC 10.1.1.2 has to send a packet to
> 10.2.1.2.
> > >
> > > The sending PC does a logical AND operation between the destination IP
> and
> > > it's subnet mask:
> > >
> > > 00001010.00000010.00000001.0000001 (10.2.1.2)
> > > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > > --------------------------------------------
> > > 00001010.00000010.00000000.0000000 (10.2.0.0)
> > >
> > > The sending PC knows that the destination IP is on network 10.2.1.0.
> > >
> > > Now the sending PC does the same with it's own IP:
> > >
> > > 00001010.00000001.00000001.0000010 (10.1.1.2)
> > > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > > --------------------------------------------
> > > 00001010.00000001.00000000.0000000 (10.1.0.0)
> > >
> > > Since the destination computer is on a different Network, the PC
cannot
> > send
> > > the packet directly to the destination, it has to send the packet
first
> to

> > > the Default Gateway. Let's say the DG in this case is 10.1.1.1. The
> > sending
> > > PC will use an ARP request to find the MAC Address of the DG. Then it
> will
> > > create a packet like this:
> > >
> > > Source MAC Address: This PC's MAC Address.
> > > Dest. MAC Address: Default Gateway's MAC Address.
> > > Source IP: 10.1.1.2
> > > Dest. IP : 10.2.1.2
> > >
> > > Since the Destination MAC Address is the Router, it will receive the
> > Frame,
> > > read the destination IP, look in its routing table and route the
packet
> > > acordingly.
> > >
> > > Keep in mind that the network mask has to be the same on all computers
> on

> > > the network (at least for the scope of Network+) and also that the
mask
> is

> > > not always 255 and 0, it can be also 128(10000000), 192(11000000),
> > > 224(11100000), 240(11110000), 248(11111000) and 252(11111100).
> > >
> > > Hope it helps.
> > > J. Rivera, CCNA, Network+, A+
> > >
> > >
> > > "captain9fingers" <spammeasmuchasyouwant@aol.com> wrote in message
> > > news:dmk3b.32$NH4.18@newsfep3-gui.server.ntli.net...
> > > > Hi,
> > > >
> > > > I'm new to this group so hello everyone

> > > >
> > > > I'm studying my network+ at the mo and something I am having
> difficulty
> > > > getting my head round is the "subnet mask" as far as I can tell the
> > reason
> > > > there is a subnet mask is so that IP knows whether the address is
> local
> > or
> > > > not.
> > > >
> > > > if I have an IP and subnet mask as follows:
> > > >
> > > > 168.168.5.3
> > > > 255.255.0.0
> > > >
> > > > Does this mean that the computer only tries to resolve the last 2
> octets
> > > > locally? Does it completely ignore the first 2 octets? If so why?
> > > >
> > > >
> > > >
> > > > If your computer has
> > > >
> > > > 168.168.5.3
> > > > 255.255.0.0
> > > >
> > > > and it wants to talk to another computer on the same network
> > > >
> > > > 168.168.7.150
> > > > 255.255.0.0
> > > >
> > > > but also have a conversation with another computer on a different
> > network
> > > >
> > > > 168.140.7.150
> > > > 255.255.0.0
> > > >
> > > > how does it distinguish between the two? The subnet masks are the
same
> > but
> > > > the 2nd octect of the IP is different but if the computer is only
> > looking
> > > at
> > > > the last 2 octects would it think the 2 computers are the same?
> > > >
> > > > Hope someone can clear this up for me cos I'm really confused.
> > > >
> > > > Thanks
> > > >
> > > >
> > >
> > >
> >
> >
> >
>
>

DaveL

2003-09-25, 12:25 am

Thank you.

Dave

"FireSword" <joxel-spamguard-@hotmail.com> wrote in message
news:P9pcb.21$VZ1.4@fe05.atl2.webusenet.com...
> Sorry, not with Partition Magic.
> The RAID Controller is where you change your set-up.
> Different Controllers let you do different things, however I don't think
you
> can just add disks to a RAID 5.
> When you write a block of data in a RAID 5, half of the block goes to the
> first disk, the other half to the second disk, and the Error Correction
Code
> goes to the third disk. Now, in the next block of data you start in the
> second disk, so the ECC goes to the first disk and so on.
> Adding a disk means that all of the data and error correction needs to be
> re-distributed again.
>
> You do have this option:
> Buy 3 larger disks.
> Replace the first disk only and wait for the system to rebuild the data on
> that disk.
> Then Replace the Second and do the same, then the third.
>
> You will end up with the same amount of space in your volume, but now it
is
> possible that your controller will let you expand the Logical
> Drive(partition).
>
> If it doesn't, you can use the extra space to create another logical
Drive,
> which you can add to the current Volume under the same Drive Letter.
> Hope this helps!
> J.
>
>
>
>
> "DaveL" <dave1027@comcast.net> wrote in message
> news:xIqcnf01_viAPe2iU-KYhA@comcast.com...
> > Thank's you are a wealth of knowledge.
> >
> > I was wondering if you can answer an unrelated question.
> >
> > If I have a raid5 with three drives and I'm running out of space, can I
> add
> > drives and run Partition magic to expand the raid to include the added
> > drives without having to back up, reinitialize the raid and restore?
> >
> > Dave
> >
> >
> > "FireSword" <joxel-spamguard-@hotmail.com> wrote in message
> > news:YYLbb.218$Fq.50@fe05.atl2.webusenet.com...
> > > Not in the example I gave..
> > >
> > > If you have a Class A Network with the mask 255.255.0.0 you can have
254[c
olor=darkred]
> > > Subnets, each with 65,534 hosts.
> > > if you change the mask to 255.255.254.0 now you have 32,768 subnets[/color]
with
> > 510
> > > hosts on each subnet.
> > >
> > > Also, remember that the number of subnets and hosts always depend on
the[c
olor=darkred]
> > > network Class you are using.
> > > For a Class C Network you can't use a mask shorter than 255.255.255.0.
> So

> > > you have to borrow bits from the last octet to create the subnets you
> > need.
> > > If you use 3 bits for subnetting and 5 for hosts, your mask is
> > > 255.255.255.224, you have (2^3)-2 = 6 subnets and (2^5)-2=32 valid
> hosts.
> > > In this case the IP 192.168.1.68 and the IP 192.168.1.132 would be in
> > > different subnets.
> > >
> > > On Cisco equipment however you can use the first and last subnet also[/color]
if
> > you
> > > want, the formula for subnets is then 2^3 = 8.
> > >
> > >
> > > "DaveL" <dave1027@comcast.net> wrote in message
> > > news:6bSdnTpgYes0_vKiU-KYvA@comcast.com...
> > > > Very nice. If I have a subnet mask of 255.255.254.0. Does that
> > > essentially
> > > > double the number of locals hosts I can have?
> > > >
> > > > Dave
> > > > A+
> > > >
> > > >
> > > >
> > > > "FireSword" <joxel-spamguard-@hotmail.com> wrote in message
> > > > news:MPb4b.228$Bc7.198@fe01.atl2.webusenet.com...
> > > > Ok, The Subnet Mask tells the computer what part of the address you
> are
> > > > using as network and what part for hosts.
> > > >
> > > > For example the default Mask for a Class A network like 10.0.0.0 is
> > > > 255.0.0.0. That implies that only the first octet is used as the
> network
> > > > part. However if you need more networks from that address, you can
use
> a
> > > > subnet mask like 255.255.0.0.
> > > > The you can have networks like 10.1.0.0, 10.2.0.0.. etc.
> > > >
> > > > Now, your pc doesn't know in which network it is. so, when it tries
to[co
lor=darkred]
> > > > "speak" to other computers it always have to compare the destination
> IP

> > > with
> > > > the network mask in order to know if the destination PC is on the[/color]
same[
color=darkred]
> > > > network. If it finds that it is on the same LAN then the packet goes
> > > > directly to the other PC, but if it finds that the destination is[/color]
not
> > form
> > > > the same network then your PC sends the packet to the Default
Gateway,
> > > which
> > > > is a router that knows how to reach the other network.
> > > >
> > > > The PC uses the binary form of the IP Address,
> > > > 10.1.1.2 is 00001010.00000001.00000001.0000010
> > > > 10.1.1.3 is 00001010.00000001.00000001.0000011
> > > > 10.2.1.2 is 00001010.00000010.00000001.0000010
> > > >
> > > > Let's say PC with IP: 10.1.1.2 , SM: 255.255.0.0 has a packet to
send
> to

> > > > 10.1.1.3.
> > > > The sending PC does a logical AND operation between the destination
IP
> > and
> > > > it's subnet mask:
> > > >
> > > > 00001010.00000001.00000001.0000011 (10.1.1.3)
> > > > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > > > --------------------------------------------
> > > > 00001010.00000001.00000000.0000000 (10.1.0.0)
> > > >
> > > > The sending PC knows that the destination IP is on network 10.1.1.0.
> > > >
> > > > Now the sending PC does the same with it's own IP:
> > > >
> > > > 00001010.00000001.00000001.0000010 (10.1.1.2)
> > > > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > > > --------------------------------------------
> > > > 00001010.00000001.00000000.0000000 (10.1.0.0)
> > > >
> > > > The sending PC is on network 10.1.0.0 also, so it can send the
packet
> > > > directly to 10.1.1.3. It uses an ARP request to find the MAC Address
> of

> > > the
> > > > Dest. PC and then creates a frame like this:
> > > > Source MAC Address: This PC's MAC Address.
> > > > Dest. MAC Address: Destination PC's MAC Address.
> > > > Source IP: 10.1.1.2
> > > > Dest. IP : 10.2.1.2
> > > >
> > > >
> > > > Now lets to the same if the PC 10.1.1.2 has to send a packet to
> > 10.2.1.2.
> > > >
> > > > The sending PC does a logical AND operation between the destination
IP
> > and
> > > > it's subnet mask:
> > > >
> > > > 00001010.00000010.00000001.0000001 (10.2.1.2)
> > > > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > > > --------------------------------------------
> > > > 00001010.00000010.00000000.0000000 (10.2.0.0)
> > > >
> > > > The sending PC knows that the destination IP is on network 10.2.1.0.
> > > >
> > > > Now the sending PC does the same with it's own IP:
> > > >
> > > > 00001010.00000001.00000001.0000010 (10.1.1.2)
> > > > 11111111.11111111.00000000.0000000 (255.255.0.0)
> > > > --------------------------------------------
> > > > 00001010.00000001.00000000.0000000 (10.1.0.0)
> > > >
> > > > Since the destination computer is on a different Network, the PC
> cannot
> > > send
> > > > the packet directly to the destination, it has to send the packet
> first
> > to
> > > > the Default Gateway. Let's say the DG in this case is 10.1.1.1. The
> > > sending
> > > > PC will use an ARP request to find the MAC Address of the DG. Then
it
> > will
> > > > create a packet like this:
> > > >
> > > > Source MAC Address: This PC's MAC Address.
> > > > Dest. MAC Address: Default Gateway's MAC Address.
> > > > Source IP: 10.1.1.2
> > > > Dest. IP : 10.2.1.2
> > > >
> > > > Since the Destination MAC Address is the Router, it will receive the
> > > Frame,
> > > > read the destination IP, look in its routing table and route the
> packet
> > > > acordingly.
> > > >
> > > > Keep in mind that the network mask has to be the same on all
computers
> > on
> > > > the network (at least for the scope of Network+) and also that the
> mask
> > is
> > > > not always 255 and 0, it can be also 128(10000000), 192(11000000),
> > > > 224(11100000), 240(11110000), 248(11111000) and 252(11111100).
> > > >
> > > > Hope it helps.
> > > > J. Rivera, CCNA, Network+, A+
> > > >
> > > >
> > > > "captain9fingers" <spammeasmuchasyouwant@aol.com> wrote in message
> > > > news:dmk3b.32$NH4.18@newsfep3-gui.server.ntli.net...
> > > > > Hi,
> > > > >
> > > > > I'm new to this group so hello everyone

> > > > >
> > > > > I'm studying my network+ at the mo and something I am having
> > difficulty
> > > > > getting my head round is the "subnet mask" as far as I can tell
the[c
olor=darkred]
> > > reason
> > > > > there is a subnet mask is so that IP knows whether the address is
> > local
> > > or
> > > > > not.
> > > > >
> > > > > if I have an IP and subnet mask as follows:
> > > > >
> > > > > 168.168.5.3
> > > > > 255.255.0.0
> > > > >
> > > > > Does this mean that the computer only tries to resolve the last 2
> > octets
> > > > > locally? Does it completely ignore the first 2 octets? If so why?
> > > > >
> > > > >
> > > > >
> > > > > If your computer has
> > > > >
> > > > > 168.168.5.3
> > > > > 255.255.0.0
> > > > >
> > > > > and it wants to talk to another computer on the same network
> > > > >
> > > > > 168.168.7.150
> > > > > 255.255.0.0
> > > > >
> > > > > but also have a conversation with another computer on a different
> > > network
> > > > >
> > > > > 168.140.7.150
> > > > > 255.255.0.0
> > > > >
> > > > > how does it distinguish between the two? The subnet masks are the
> same
> > > but
> > > > > the 2nd octect of the IP is different but if the computer is only
> > > looking
> > > > at
> > > > > the last 2 octects would it think the 2 computers are the same?
> > > > >
> > > > > Hope someone can clear this up for me cos I'm really confused.
> > > > >
> > > > > Thanks
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> > >
> >
> >
>
>
>[/color]

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