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Advanced LAN setup...


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#1
computerspecialist101

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Greetings,

I have a very complicated networked setup that I would like some help with to make it better. I am hoping that what I am trying to do will be possible with what I have, but if it is not, let me know and I will leave it alone or possibly find another way of doing what I want done with an investment in new hardware.

I would prefer to have experienced networkers commenting only as I am trying to avoid having users that don't know much about networking trying to post something that is far off from working.

Now onto what I am working with. I have a SonicWall Pro-VX that is the first device after my cable modem that the internet will see. Link to info about SonicWall Pro-VX) (SonicWall Family Manual). I have a cable running to a Linksys WRT54G router that is sending a wired signal to my basement which houses my server which hosts my website and my FTP service. Then another cable is running off of the Linksys router to another PC which uses the VPN service from the sonicwall firewall. Then off of the Linksys router again, it is sending a wireless signal to the second floor where I am capturing the signal by a Buffalo bridge and converting the wireless to wired signals and passing the connection straight through without changing the IP address changes. (I will talk more about the IP address info later, as that is what this is all about.)

The way that I have the IP addresses set up is that the sonicwall unit is receiving a wan ip address from the cable modem as 66.XXX.XXX.XXX and then sending out an ip address of 192.168.168.168 for a WAN ip address to the Linksys which then has a default gateway ip address of 192.168.1.1 and passing out DHCP and Static ip address on the 192.168.1.XXX range. when the linksys router sends the wireless signals to the buffalo bridge, the bridge is acting like a passthrough and gets an ip address of 192.168.1.55, but gives any ip address that is connected to it either static or DHCP address on the range of 192.168.1.XXX which is assigned from the linksys router.

Right now i have file sharing going on between all three computers connected to the whole setup. the most important file sharing that i need to have is between my server and my computer, which is on the second floor. The sonicwall unit has a Wan port, a DMZ port, and a LAN port for your reference. Here are my goals:

  • To have the most secure setup that i can have to limit the chance that a hacker can gain access to my network, my website, and my FTP server as well as any othe computers on the network.
  • To be able to shared drives between all computers on my network, including between the server and my computer upstairs.
  • To be able to have my linksys router act as a pass through and have the sonicwall assign ip address with its built in DHCP server, or static ip addresses. I do understand that the new ip address will be on the 192.168.168.XXX range, which will be fine.
  • continue to have wireless internet is a MUST.
I also have a small 5 port switch where one of the ports will act as the WAN port and the other four will act as the LAN port. I have a small budget that i can spend on getting more hardware to get it working with my goals, so i would like to not have to spend anything else on this to get it working.

I appreciate any of your help.

Thanks,

Mike Wohlrab
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#2
hfcg

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Hello,
I am a little bit confused, What is the nature of the problem you are having?
What is your question?
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#3
computerspecialist101

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Greetings,

I thought I was clear, but i will elaborate a little bit more. the sonicwall firewall has a built in dhcp server that i would like to utilize so i can send out ip addresses on the 192.168.168.XXX range, but i also need wireless, which is being provided by the linksys. the problem is that i dont know how to configure it so that the linksys router will be able to send wireless internet around and have any computers that are connected to it be assigned an ip address of 192.168.168.XXX, which would be assigned by the sonicwall firewall.

If you still do not get what i am trying to do, can you elaborate on what you are not getting about what i am trying to do.

Thanks for responding,

Mike Wohlrab
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#4
hfcg

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Subnet Addressing



By Ron Cooney

Questions regarding this article should be sent to the author at ron.cooney@paranet.com .

The issue of subnetting has long been a mystery to many system administrators. It seems that there are just too many bits, bytes, and masks involved to make it worthwhile. Besides, who needs all that trouble when it's all you can do to just maintain the network as it is? You can certainly find sympathy, but if your network plans call for Internet access then IP (Internet Protocol) addressing and possibly subnet masking are topics that you s hould be familiar with.

As networks grow to increasing numbers of segments, more network address numbers will be needed as each segment requires an individual number. The InterNIC (whose name signifies cooperation of Network Information Centers or NICs), however, is not eager to hand out unlimited network addresses because they are quickly running out of them. The Internet community is generally taking a firm stand on limiting address availability, due to the accelerated growth demand for Internet access. Network administrators will have to work with what they have to better accommodate network requirements and the shrinking supply of address numbers.

One way of accomplishing this address conservation is to take the address that is assigned to your network and expand the capacity with subnets. Subnetting allows you to increase the number of networks available to you without applying for another IP address number.

IP Addressing
The IP addressing framework allows one to address about 16,000,000 unique hosts for a Class A address, around 65,000 hosts for a Class B address, but only 254 hosts for a Class C address. However, there are no more Class A addresses available, and the InterNIC has stopped assigning Class B addresses. Class C addresses are the most numerous, but their limitation is that each can identify only 254 unique hosts.

The IP address is composed of 32 bits, which consist of two parts: the most significant bits (MSBs) identify a particular network and the remaining bits specify a host on that network. The most significant bits of the network portion actually determine the address class as shown in this table:

Address MSB
Class Pattern
Class A 0
Class B 10
Class C 110

Class A Address Example
A class A address could be diagramed:

Network Host
+------+ +----------------------+
| | | |
[0xxxxxxx][xxxxxxxxxxxxxxxxxxxx
xxxx]

which shows the eight network bits followed by the 24 host bits.

These 32-bit IP addresses are almost always written as four dot-separated decimal numbers, one for each byte of the address. Thus, our class A address would have a range of address numbers from 1.0.0.0 through 126.0.0.0 ( 0. x.x.x and 127. x.x.x are reserved). The number of host addresses per network is 16,777,214, which is two less than two raised to the 24th power because both host numbers 0.0.0 and 255.255.255 are reserved.

In practice, people don't really attach 16 million hosts to a network so administrators of a Class A site often divide the host address portion into a (sub)network and host portion. (Subnetting is now supported by most operating systems.) Each Class A network number can support up to 65,534 subnets (network numbers 0.0 and 255.255 are reserved) with each having 254 hos ts (host numbers 0 and 255 are reserved). This is done by using the 16 high -order bits of the host portion for the subnet number and the lower eight bits for the host as diagramed here:

Network Subnet Host
+------+ +--------------+ +------+
| | | | | |
[0xxxxxxx][xxxxxxxxxxxxxxxx][xxxxxxxx]

Class B Addresses
The first two bits of a Class B address are 1 and 0, the next fourteen bits identify the network and the last sixteen the host, as diagramed:

Network Host
+--------------+ +--------------+
| | | |
[10xxxxxxxxxxxxxx][xxxxxxxxxxxxxxxx]

Thus, Class B addresses include the network numbers in the range from 128.1.0.0 through 191.254.0.0 for a total of 65,534 host addresses.

As with the Class A address, we can divide the host portion of a Class B address into subnet and host parts. For instance, let's spli t our Class B network number on the byte boundary, that is, the eight MSBs of the host portion identifies the subnet and the remaining bits the host, as diagramed:

Network Subnet Host
+--------------+ +------+ +------+
| | | | | |
[10xxxxxxxxxxxxxx][xxxxxxxx][xxxxxxxx]

This arrangement allows 254 subnets each with 254 hosts.

Other Address Classes
The first three bits of a Class C address are 1, 1, and 0, the next 21 bits identify the network and the last eight the host, as diagramed:

Network Host
+----------------------+ +------+
| | | |
[110xxxxxxxxxxxxxxxxxxxxx][xxxxxxxx]

Thus, Class C addresses include the network numbers in the range 192.0.1.0 through 223.255.254.0 for a total of 254 host addresses per network address.

Finally, we have Class D and Class E addresses. Class D address start at 224.0.0.0 and are used for multicast purposes. Class E addresses start at 240.0.0.0 and are currently used only for experimental purposes.

The Subnet Mask
A subnet mask (or number) is used to determine the number of bits used for the subnet and host portions of the address. The mask is a 32-bit value that uses one-bits for the network and subnet portions and zero-bits for the host portion.

Let's look at an example. Here we have a Class B address of 191.70.55.130 and apply some different subnet masks. A logical AND operation is performed between the IP address and the subnet mask as shown:

Here we use a mask that retains the default 16 network and host bits for a Class B address:

191 70 55 130
1011 1111 1000 0110 0011 0111 1000 0010 IP address
1111 1111 1111 1111 0000 0000 0000 0000 Subnet mask
1011 1111 1000 0110 0000 0000 0000 0000 Result

Here we employ a mask that d ivides the host portion into a subnet and host that are each eight bits wide:

191 70 55 130
1011 1111 1000 0110 0011 0111 1000 0010 IP address
1111 1111 1111 1111 1111 1111 0000 0000 Subnet mask
1011 1111 1000 0110 0011 0111 0000 0000 Result

This division allows 254 (256-2 reserved) subnets, each with 254 hosts.

This division on a byte boundary makes it easy to determine the subnet and host from the dotted-decimal IP address. However, the subnet-host boundary can be at any bit position in the host portion of the IP address. Here, we use a mask that allows more subnets (512-2 reserved), but with the trade-off of fewer hosts (128-2) per subnet:

191 70 55 130
1011 1111 1000 0110 0011 0111 1000 0010 IP address
1111 1111 1111 1111 1111 1111 1000 0000 Subnet mask
1011 1111 1000 0110 0011 0111 1000 0000 Result

The subnet-host number t radeoff
Here's a table that let's you see at a glance the trade off between the number of subnets and hosts with different subnet masks for both Class B and Class C addresses. We've already subtracted two from the results in the last two columns to take the reserved network and host numbers into account:

Class B Subnetting:

# Mask Bits Subnet Mask # Subnets # Hosts
2 255.255.192.0 2 16382
3 255.255.224.0 6 8190
4 255.255.240.0 14 4094
5 255.255.248.0 30 2046
6 255.255.252.0 62 1022
7 255.255.254.0 126 510
8 255.255.255.0 254 254
9 255.255.255.128 510 126
10 255.255.255.192 1022 62
11 255.255.255.224 2046 30
12 255.255.255.240 4094
14
13 255.255.255.248 8190 6
14 255.255.255.252 16382 2

Class C Subnetting:

# Mask Bits Subnet Mask # Subnets # Hosts
2 255.255.255.192 2 62
3 255.255.255.224 6 30
4 255.255.255.240 14 14
5 255.255.255.248 30 6
6 255.255.255.252 62 2

The Subnet Advantage
Subnetting hides the internal network organization to external routers and thus simplies routing. For instance, a subnetted Class B address would require fewer routes than the equivalent number of Class C addresses. Shorter routing tables mean faster network transfers.

Subnetting allows address administration to be decentralized. Besides technical advantages, this approach may also provide political benefits for the organization. For instance, an administrator could assi gn a subnet to a department, which would then be responsible for their own network management.

Subnetting can help overcome distance limitations of physical networks by dividing up a physical network into individually addressed networks so they can be connected logically with routers.

Example: Subnetting a Class C Network
One of the first things a network administrator needs to do is define the requirements for the network. The logical place to start is to consider how many hosts are on the network.

Using the maximum number of hosts on one Ethernet segment is generally not good practice because it could create performance problems due to network congestion. If you only have one Class C address assigned to your network then what can you do? Refer to our table above that depicts the Class C address subnetting network number-host trade off.

Even though a Class C address can support up to 254 hosts, in my experience, 60-80 hosts is a good number for most LANs using of fice automation tools. I've seen overloaded Ethernet segments--with over 100 hosts--at client sites. My recommendation is that they segment their LAN in half or even further. Also, many hub cards come with 24 ports per card, which makes it easy to segment in 24-host multiples provided that the hub supports multiple segments on the backplane. Many do.

One reasonable approach would be to select six subnets each with 30 hosts. Although two subnets with 62 hosts is also feasible, it is not as flexible because there are only two subnets. The other alternatives that use more subnets probably don't provide enough hosts per subnet.

Subnets 0 and 7 are unusable because they are used for special addressing situations. For instance, a subnet of 7 (all one bits) is reserved for an all subnets-directed broadcast (a broadcast sent to all subnets of the specified subnetted network) when the host bits are all one. This leaves subnets 1 through 6 available for use.

In each subnet, the first ho st number (0) is reserved, and the resulting number is known as the network number. The last number in each subnet is reserved for the broadcast address, and cannot be used for a host address. Consequently, in this case there are only 30 host addresses available for each subnet.
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#5
computerspecialist101

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Greetings,

Thanks for the reply. It has great information. But can you help with setting it up correctly with my firewall and routers, and other stuff i have. All that i got out of that told me how it helps and how it works, but it didnt tell me how to set up my network to make it work.

Thanks,

mike
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#6
hfcg

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What you need to do is set up a subnet.
Each of your computers will be on the subnet of the network.
Here is a handy tool to help you.
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#7
hfcg

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Are you setting up a network for a business?
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#8
computerspecialist101

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Greetings,

I am setting it up for a business, my own comapny. What settings do i need to change in my sonicwall and linksys units to get the result. like what do i take from the calculator and where do i put it in my soinicwall and linksys. Ive done some advanced setups with networking, but im not that farmiliar with it to do what i want.

Thanks,

mike
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#9
hfcg

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I have given this some thought, and I am sorry but I am not going to help you.
My time is better spent helping some one that has a problem, not some one trying to set up a network for their business.
I gave you a push in the right direction. Now it is up to you to set up the subnet.
If you can not do the research involved than I would like to suggest that you hire a good company to do this for you.
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#10
computerspecialist101

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OK, thanks for the help you did give.

Mike

Edited by computerspecialist101, 03 February 2008 - 10:44 PM.

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