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Subnet mask problem? 2
- Thread starter tbalazs
- Start date
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1
- #2
Nope.
In theory that is supposed to be used by class A hosts running IP Addresses from 1.0.0.1 to 126.255.255.254 but anyone can use any net mask as long as it allows you to see the other addresses you need to. Yours is kind of overkill as it allows you to see rather more computers on the same network than you will ever need.
In theory that is supposed to be used by class A hosts running IP Addresses from 1.0.0.1 to 126.255.255.254 but anyone can use any net mask as long as it allows you to see the other addresses you need to. Yours is kind of overkill as it allows you to see rather more computers on the same network than you will ever need.
I would change it to the correct subnet mask. I can see where you might out a new piece of equipment on the wire and it would not *let* you choose an illegal subnet mask for the range. Then what do you do? Sounds like an accident waiting to happen ( at the worst time)
Just my opinion
Mike S
Just my opinion
Mike S
What is your current IP address cheme?
For your mask, each client would need the same first octet of the IP address. If you changed the mask to 255.255.255.0 then each client would need to have the same first three octets. Doug
dxd_2000@yahoo.com
For your mask, each client would need the same first octet of the IP address. If you changed the mask to 255.255.255.0 then each client would need to have the same first three octets. Doug
dxd_2000@yahoo.com
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- #5
The subnet Mask gives you the Part of the Network Address.
All Bits set describe this Part.
The Bits not set describe the Computer Address. That means dependent on the amount of your computers, Network Printers, X-Terminals etc. you have to select your Mask.
Subnet Mask 255.255.255.0 (Class C Network) allows you 254 Network Nodes. The Node Address with all Bits set (255) is not allowed because it is the Broadcast address. Also Address 0 is not allowed for Network nodes.
Be aware Network addresses with first octet >223 are class D Addresses which are not supported in many cases. It is for experimental purposes only.
hnd
hasso55@yahoo.com
All Bits set describe this Part.
The Bits not set describe the Computer Address. That means dependent on the amount of your computers, Network Printers, X-Terminals etc. you have to select your Mask.
Subnet Mask 255.255.255.0 (Class C Network) allows you 254 Network Nodes. The Node Address with all Bits set (255) is not allowed because it is the Broadcast address. Also Address 0 is not allowed for Network nodes.
Be aware Network addresses with first octet >223 are class D Addresses which are not supported in many cases. It is for experimental purposes only.
hnd
hasso55@yahoo.com
- Thread starter
- #7
You could not put those live on the Internet then!
Are they all manually configured at the client or are they assigned automatically by DHCP?
Depending on the no of comps I would recommend going DHCP if you change computers much. Static IP is ok for about 5 to 10 computers, more than that and I would recommend DHCP if you can - simplifies things.
If you only have a few, then manually change them to:
192.168.0.x starting at 1 and going upwards by 1 each time.
Subnet mask 255.255.255.0 for each.
If you want to go DHCP, let me know...
Are they all manually configured at the client or are they assigned automatically by DHCP?
Depending on the no of comps I would recommend going DHCP if you change computers much. Static IP is ok for about 5 to 10 computers, more than that and I would recommend DHCP if you can - simplifies things.
If you only have a few, then manually change them to:
192.168.0.x starting at 1 and going upwards by 1 each time.
Subnet mask 255.255.255.0 for each.
If you want to go DHCP, let me know...
- Thread starter
- #9
We have about 18 PCs on the LAN but this is planned to increase, maybe to 30 max. for a while. Are there potential implications for progs such as Outlook, which communicate with a mailserver via TCP/IP, in moving to DHCP? Also software firewalls? (Currently use ZoneAlarm with named IP address as local and/or trusted).
Your feedback has been extremely helpful. Thank you.
Tony.
Your feedback has been extremely helpful. Thank you.
Tony.
Hey Mike,
Correct me if I'm wrong but wouldn't that large of a subnet mask make the IP stack think it doesn't need to use the router to reach a large number of addresses? I would think that using that large of a subnet mask would cause connectivity problems for addresses very close to their IP range.
GJ
Correct me if I'm wrong but wouldn't that large of a subnet mask make the IP stack think it doesn't need to use the router to reach a large number of addresses? I would think that using that large of a subnet mask would cause connectivity problems for addresses very close to their IP range.
GJ
GJ-
I have one network that runs a full class A ( not legal) among a couple thousand nodes. The nice thing about TCP and subnetting is the fact it's binary. It works or not. I have not seen in a "properly" configured network where you can not place to addresses adjacent and not have them work.
A rough discription of this network is 4 site with many remote sites. One primary site has the class A plus class B PLUS class C addresses on the same site. Most wan links are class B and the 3 other sites are class B. Most remote sites are class C. With all the subnetting, there are over 250 subnets. Not surprisingly, this network is something of a handful to manage at times.
The point is that I have placed many IPs adjacent and they work fine.
Whether to use a router is dependent on if there is a default gateway declared on the client.
Mike S
I have one network that runs a full class A ( not legal) among a couple thousand nodes. The nice thing about TCP and subnetting is the fact it's binary. It works or not. I have not seen in a "properly" configured network where you can not place to addresses adjacent and not have them work.
A rough discription of this network is 4 site with many remote sites. One primary site has the class A plus class B PLUS class C addresses on the same site. Most wan links are class B and the 3 other sites are class B. Most remote sites are class C. With all the subnetting, there are over 250 subnets. Not surprisingly, this network is something of a handful to manage at times.
The point is that I have placed many IPs adjacent and they work fine.
Whether to use a router is dependent on if there is a default gateway declared on the client.
Mike S
Hey Mike,
I actually have seen communications problems between two ips that were very close together when one machine had a too small network mask. It thought the other machine was on a different segment and was trying to reach it through the router which wouldn't work.
I was referring to the opposite case where if his IP is 10.0.0.10 and he's trying to communicate with 10.0.10.10, his subnet mask indicates he's on the same subnet and communication via the router is not necessary. If he's on a class c, then we know that the router is required but he won't be sending packets to the router.
I didn't mean that 10.0.0.10 would have trouble with 10.0.0.12, I meant close as in 10.0.0 close to 10.0.1, 10.0.2, etc.. that are inside the bogus class a. If his lan is not connected to the Internet, then there's no problem but I was under the impression this was connected to a larger legitimate network.
btw, thanks for the info on the sniffer software, I didn't get a chance to check them out yet. Do you find they work as well as real sniffers like Data General & such?
GJ
I actually have seen communications problems between two ips that were very close together when one machine had a too small network mask. It thought the other machine was on a different segment and was trying to reach it through the router which wouldn't work.
I was referring to the opposite case where if his IP is 10.0.0.10 and he's trying to communicate with 10.0.10.10, his subnet mask indicates he's on the same subnet and communication via the router is not necessary. If he's on a class c, then we know that the router is required but he won't be sending packets to the router.
I didn't mean that 10.0.0.10 would have trouble with 10.0.0.12, I meant close as in 10.0.0 close to 10.0.1, 10.0.2, etc.. that are inside the bogus class a. If his lan is not connected to the Internet, then there's no problem but I was under the impression this was connected to a larger legitimate network.
btw, thanks for the info on the sniffer software, I didn't get a chance to check them out yet. Do you find they work as well as real sniffers like Data General & such?
GJ
::the light goes on::
Ahhh.. you are talking about overlapping subnets? Where you might have a client with a 126.0.0.10 address/mask of 255.0.0.0 and a 2nd client on the same wire with a 126.0.0.20 address/mask of 255.255.255.0 ? yes,, that is a no-no in the world of IP masking ( mostly) some folks do it because they can get away with while they remember what they have done and where. It's not recommended by everyone I've talked to since my network does have this "problem" leftover from the previous geek.
Data General Sniffer is no more.. they were purchased quite a while ago by NAI and merged with NetXray to make SnifferPro. Etherpeek is a slightly different program in how it presents the data vs. Sniffer. They both do the same thing.. and both are very good at what they do. Each has it's advocates but the differences are pretty subtle to many of us. If I used it as a primary tool daily, I might have a differrent opinion.
Mike S
Ahhh.. you are talking about overlapping subnets? Where you might have a client with a 126.0.0.10 address/mask of 255.0.0.0 and a 2nd client on the same wire with a 126.0.0.20 address/mask of 255.255.255.0 ? yes,, that is a no-no in the world of IP masking ( mostly) some folks do it because they can get away with while they remember what they have done and where. It's not recommended by everyone I've talked to since my network does have this "problem" leftover from the previous geek.
Data General Sniffer is no more.. they were purchased quite a while ago by NAI and merged with NetXray to make SnifferPro. Etherpeek is a slightly different program in how it presents the data vs. Sniffer. They both do the same thing.. and both are very good at what they do. Each has it's advocates but the differences are pretty subtle to many of us. If I used it as a primary tool daily, I might have a differrent opinion.
Mike S
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