Software

Ask something
Question Locked

subnetting

0 helpful
10 replies

by psu70433

Closed to new repliesThis discussion is closed. It stays readable, but it takes no new replies.

New to this, our corp office asked for a new public IP block from our provider. We were given:

208.34.31.192- 208.34.31.255 /26

We have 6 sites to configure so asked the provider how this will work. They replied: "The request lists one /26. This however can be further subnetted for eight locations with six usable IPs each, or eight /29s. The routing determines which /29 goes to which circuit."

Can anyone explain to me who to break this up? What are they talking about and how can I do this?

thanks in advance

10 replies

by wancona

It's hard to explain, but I know a little about subnetting from school.

The 8 new networks in which you will have is
208.34.31.192 / 255.255.255.248
208.34.31.200 / 255.255.255.248
208.34.31.208 / 255.255.255.248
208.34.31.216 / 255.255.255.248
208.34.31.224 / 255.255.255.248
208.34.31.232 / 255.255.255.248
208.34.31.240 / 255.255.255.248
208.34.31.248 / 255.255.255.248

.31.192 network = .31.192 broadcast = .31.199
.31.200 network = .31.200 broadcast = .31.207
.31.208 network = .31.208 broadcast = .31.215
.31.216 network = .31.208 broadcast = .31.223
.31.224 network = .31.208 broadcast = .31.231
.31.232 network = .31.232 broadcast = .31.339
.31.240 network = .31.240 broadcast = .31.247
.31.248 network = .31.248 broadcast = .31.255

I'm not sure how to configure the routers, but these are your available networks.

Each network only allows for 6 host. The ip address above each has to have a network address and a broadcast address, so that takes 2 possible ip addresses from the intial 8 leaving you 6 host address available.

by cg it

because these are public addresses from the ISP. Often ISPs won't let you subnet their public addresses. Your assigned specific addresses or a block of addresses and you can't change them because doing so might cause a conflict with other hosts on their network that might have been assigned those addresses.

Though wancona is correct in the subnetting, what the list shown is, is a block of addresses. I'd check to make sure that you can use the block of addresses before doing so.

by wancona

I was wondering about that too, because normally they would use a NAT table to convert from the internal ip address to the ISP's external ipaddress. But he said that he asked for a block of time, and they told him to subnet it using /29.

by wancona

Isn't subnetting just pretty much taking the address already given to you and breaking it down into smaller networks, but they still fall under the same network that was assigned by the ISP.

Here is the example that I'm thinking,
C:
-- \Program Files
---- \Application
-- \Windows
---- \System32

Just an example, but wouldn't all the files and folders still fall under the same C: drive. Just as all subnets fall under the original network address. Again, I'm still in school for this, I know how to subnet, but not all the way certain on why in certain situations.

by bart777

I would have to assume that you are not familiar with IP subnetting at all.

Ok, a couple of basics.

The subnet mask divides the network address from the host address.

The /26 they are referring to is the subnet mask. They are telling you that they are giving you a 26 bit subnet mask. EX. 255.255.255.0 is a 24 bit mask.

The second thing that tey are saying is that if you increase the subnet length you can get more networks with fewer hosts.

Here is a link to a nice basic description of what I'm referring to.http://www.enterprisenetworkingplanet.com/netsp/article.php/3566521
Take a read thru it and see if you understand what they're talking about. IF you are still having issues do a quick google search for submetting 101 and read some of those links.

Best of luck

by bogsibogs_102002

hello, based on what Ive done before dealing with ISPs they only give you a set of IP addresses that you can used. Ex. your company bought 4 static IP (public ip) ISP will give you 4 static IP corresponding to 1 subnet only then additional to these is the free fake IPs use for connection only (these one optional if you have VPN). End user will not anymore make some subnetting all you need to do is assign this static ips to (1) your router interface connecting to ISP (2) servers like Web server, DNS server or any server that you want to exposed in the net for them to become accessible outside your LAN. ISP will provide also a username and password that you will log in your router but it is depending on your ISP policies. hope this experience can give some info.

by cg it

from the host portion of the address to create the subnet.

But I question whether the poster's ISP told them to subnet their public addresses. I can't see an ISP doing that. They either give you a block of public addresses to use or your get 1 address. Either DHCP assigned or a static address[s].

by wancona

I understand what you mean, I actually didn't think they would either. He should probably look into NAT tables

by psu70433

All infomation was helpful and the ISP did allow us to subnet the /26 block into (8) /29 blocks.

This discussion is closed to new replies.