A subnetwork, or subnet, is a logically visible subdivision of an IP network. The practice of dividing a single network into two or more networks is called subnetting and the networks created are called subnetworks or subnets.

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How does IPv4 Subnetting Work?

This is a Canonical Question about IPv4 Subnets. Related: How does IPv6 subnetting work and how does it differ from IPv4 subnetting? How does Subnetting Work, and How do you do it ...
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6answers
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CIDR for Dummies

I understand what CIDR is, and what it is used for, but I still can't figure out how to calculate it in my head. Can someone give a "for dummies" type explanation with examples?
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3answers
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How does IPv6 subnetting work and how does it differ from IPv4 subnetting?

This is a Canonical Question about IPv6 Subnetting. Related: How does IPv4 Subnetting Work? I know a lot about IPv4 Subnetting, and as I prepare to (deploy|work on) an IPv6 ...
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6answers
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Is X.Y.Z.0 a valid IP address?

Are IP addresses with a 0 in the last octet valid? 10.6.43.0 In my case, I have the the following netmask 255.255.252.0 What about a 0 for the other octets?
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What are the implications of having two subnets on the same switch?

Can anyone tell me what some of the implications of having two different subnets on the same switch would be if VLANs are not being used?
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2answers
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Connecting to a remote server through a VPN when the local network subnet address conflicts with a remote network

This is a Canonical Question about solving IPv4 subnet conflicts between a VPN client's local network and one across the VPN link from it. After connecting to a remote location via OpenVPN, ...
18
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8answers
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What is the network address (x.x.x.0) used for? [duplicate]

It appears to be common practice to not use the first address in a subnet, that is the IP 192.168.0.0/24, or a more exotic example would be 172.20.20.64/29. The ipcalc tool I frequently use follows ...
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4answers
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Best way to segment traffic, Vlan or subnet

We have a medium sized network of around 200 nodes and are currently in the process of replacing old daisy chained switches with stack-able or chassis style switches. Right now our network is broken ...
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8answers
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When/why to start subnetting a network?

Under what conditions does one start to consider subnetting a network? I'm looking for a few general rules of thumb, or triggers based on measurable metrics that make subnetting something that should ...
17
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3answers
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Is it possible to SSH access a server with a misconfigured subnet?

We have a server where one of our engineers misconfigured the subnet and now we are locked out of this server and the only access that I know of would work is a serial console from IDC (it means ...
10
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3answers
862 views

Creative IP/subnet/dns schemes

I've only administered rather small networks (<=25 nodes). Usually I put the gateway .1, dns/proxy as .10, mail at .20, printers at .30-39 and so on and so forth. I never directly use IP addresses ...
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4answers
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What are the implications of expanding an internal subnet mask?

Our network is currently working on a 192.168.0.x subnet, all controlled through DHCP, except for the few main servers who have hard-configured IP address settings. What would I kill if I changed the ...
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4answers
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multiple physical interfaces with IPs on the same subnet

I have a linux box with 9 NICs on it, and I want eight of them to have unique addresses on the same subnet, e.g.: ifconfig eth1 192.168.123.1 netmask 255.255.0.0 ifconfig eth2 192.168.123.2 netmask ...
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4answers
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Wake on LAN over different subnets

I have 3 IP blocks and 3 Cisco Switches. Each switch has its own IP block - 10.45.100.0/24, 10.45.101.0/24 and 10.45.102.0/24 I have got a PC on 10.45.100.0/24 block. I can wake up whole computers ...
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1answer
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Proxmox - single public ip with multiple vms, openvz containers work, kvm's don't have a route

Currently I only have a /30 block (1 usable IP) (I just ordered a /28 for 13 usable publics, waiting) I just installed proxmox, set up a few virtual containers. Port forwarded the necessary ...
0
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1answer
295 views

Using a CIDR range as a Routed Subnet?

I have a /29 subnet assigned by my ISP, with an SonicWALL office router and a Cisco voice router hooked up to a 'net-rail' of sorts with untagged VLAN switch ports connecting my ISP router's output ...
11
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2answers
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Multiple VLANs, multiple subnets, single DHCP server?

At my job we are prepping to transition from multiple LANs connected over slow VPN connections to a single MAN connected over fiber, and I've got a few questions. First of all, we are planning on ...
6
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3answers
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Changing netmask from /24 to /16 on a Windows 2003 domain

I have a Windows 2003 domain using 192.168.0.0/24 with all static addresses (no dhcp). I want to move to 192.168.0.0/16 because we need more addresses. I understand that we need to change netmask ...
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5answers
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A website hosted on the 1.0.0.0/8 subnet, somewhere on the Internet?

Background I'm attempting to demonstrate, using a real-world example, of why someone would not want to configure their internal network on the 1.0.0.0/8 subnet. Obviously it's because this is not ...
4
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3answers
7k views

How to configure remote access to multiple subnets behind a SonicWALL NSA 2400

I have a client that uses a SonicWALL NSA 2400 as their firewall. I need to setup a second LAN subnet for a handful of PC. Management has decided that there should be a second subnet even though ...
2
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2answers
2k views

Hazards of increasing network size by changing the netmask

We are running a small network with address range 192.168.0.0/24. So we only have 254 IPs available. We want to increase this range slightly, to allow more hosts in the network. So if I change the ...
2
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4answers
5k views

How to make sharing possible between two different subnet computers

I have USB drive Internet on my one laptop and I have enable the ICS on that and from LAN of laptop I am asharing Internet with router, which then used by other laptops The static ip of Laptop LAN is ...
3
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2answers
548 views

Extending a subnet

We currently have a private IP subnet using the 192.168.1.0/24 range. We are running out of IP addresses and would like to extend this subnet, to something like 192.168.0.0/21. Is it possible to do ...
2
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4answers
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Subnet calculator for MS Excel

I quite often use the handy subnet calculator here: http://www.subnet-calculator.com/ Which I find very useful. However, does anyone have details/a link for a version of this that offers similar ...
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4answers
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Can I use a subnet mask to limit the number of users on a router?

(I'm not a network guy, so please humor me.) I want to configure a typical consumer router as an open hotspot. However, the router's internet connection has limited bandwidth. Therefore, I'd like to ...
0
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2answers
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KVM with one host IP and a different subnet for machines

I've already setup a KVM host with proper IP configurations, but my host had me create DHCP and use that to assign the IP's to the machines. I want to see if there's an easier way to do it (or ...
0
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4answers
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Finding the first and last address of a block of IP addresses with subnet mask

I am not sure if this is the right place to make this question but I thought this is one of the most appropriate SE's site to make a question on networking. Please move it to other more appropriate ...
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2answers
925 views

One big subnet with all clients an issue?

Disclaimer: Network rookie, might have wrong assumptions. Got a basic subnet question that im interested in hearing your thoughts about. Subnet: 192.168.251.0/24 Address Range for servers: ...
2
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2answers
228 views

How to get a report of all mac addresses on another subnet?

We have an MPLS consisting of two branches: Location1 and Location2. I am using the Softperfect netscan to report all ip addresses and mac addresses of devices on Location1 where my workstation is ...
2
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3answers
4k views

Force Windows Local Subnet Traffic through a Gateway

We are attempting to route all traffic from a certain machine to a gateway. This works ok for traffic destined for subnets outside of the machine's subnet. However, traffic to machines in the same ...
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1answer
137 views

Can I split my colo WAN subnet? /27

I recently started colocating at a datacenter, and they provided me with a /27 subnet, let's say 192.0.2.112/27 , this translates to usable IP's .96 to .127. Because of a requirement in my network, ...
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1answer
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VPN into multiple LAN Subnets

I need to figure out a way to allow access to two LAN subnets on a SonicWall NSA 220 through the built-in SonicWall GlobalVPN server. I've Googled and tried everything I can think of, but nothing has ...
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1answer
650 views

How to add IPs to a CentOS Server?

I wanted to know how to add the Prefix, the usable range & the subnet mask. I'm a completely new to this field so I would need step-by-step instructions. Thanks in advance. Regards, Netizen P.S. ...
0
votes
1answer
143 views

Make Asterisk to serve another subnet

I have server with Linux Ubuntu 12.04. It has two subnets - 192.168.0.1(eth0) and 192.168.1.1 (eth1). There is an Asterisk server (IP PBX) connected to first subnet, lets say it has IP address ...
0
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1answer
494 views

'IPv6' Newbie with IPv6 address assigment

I am new to IP v6 and I am looking to translate some existing private IPv4 addresses into v6 address assignment. Can someone please help me to answer/explain the questions below? If I have an v4 ...
0
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3answers
400 views

IP Address Planning for our Network

We have a /24 IP Address range for PCs containing 240 allocated addresses at the moment. Our company is planing for expansion of another 50 PCs, our existing IP range is 192.168.8.0/24 Do we add on ...
0
votes
3answers
8k views

How to reach a device on a different subnet?

I have what may seem to be a basic question about routing, but I ask it because I am not sure where to start. I have a simple network setup: Client1, Win7, 192.168.0.50, default gateway is set as ...
0
votes
2answers
17k views

Unable to query LDAP server on port 389 on the Win2K domain controller from a different subnet

I have a rather puzzling problem with the LDAP access to Active Directory in a Windows domain. The configuration is as follows: There are two main networks: 192.168.0.0/24 and 192.168.100.0/24 These ...
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votes
3answers
2k views

Packets dropped due to NAT? Firewall? Unroutable private IP addresses?

Preliminary note This question is out of academic interest. I know how to work around the limitation. I use this setup to control access from one subnet to the other on IP level which works great so I ...