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 ...
73
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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 ...
27
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6answers
20k views

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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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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3answers
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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, ...
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6answers
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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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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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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 ...
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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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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 ...
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3answers
1k 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
9k views

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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1answer
6k views

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 ...
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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
337 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
1k views

IPv6 subnetting a /64 - what will break, and how to work around it?

In IPv6, you are not supposed to subnet to anything smaller than a /64 (RFC 5375). Among other things, SLAAC does not work with smaller subnets, and apparently also some other features will break. ...
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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 ...
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3answers
4k views

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 ...
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3answers
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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 ...
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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 ...
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4answers
7k 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 ...
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3answers
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Sonicwall routing between multiple subnets on multiple interfaces

As shown by the network diagram below, I have two completely separate networks. One is being managed by a Sonicwall NSA 220, the other by some other router (the brand is not important). My goal is to ...
3
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2answers
616 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 ...
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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
5k views

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
3k views

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
20k views

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
1k 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: ...
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2answers
153 views

Potential traffic issues on one big(ger) subnet

Posts like this: Most traffic in a corporate LAN is client to server nowadays, and a router not very well setup rather becomes a bottleneck AND a SPOF. and 200+ clients on a subnet wasn't a ...
2
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2answers
311 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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0answers
33 views

Small business network vlans and hyper-v configuration

We are a small business and have been successfully running one Hyper-V 2012 R2 vmhost with many Windows Server 2012 VMS that includes a DC, Web Server, CRM Server and SQL Server for a couple of years. ...
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1answer
132 views

Can I set up a VoIP phone to connect to it's gateway over VPN with different subnets?

A little background first: Currently, we have a main office and a remote office. They are connected via site-to-site VPN. Main office uses a Cisco router with DHCP at 10.10.10.0/24 while the remote ...
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1answer
167 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
4k views

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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3answers
11k 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 ...
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1answer
677 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. ...
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vote
1answer
675 views

How to route VoIP phone through VPN

We have two offices (China and US) connected by site-to-site VPN using 2 Linksys RV082's. We also have a VoIP system with 2 VoIP phones in the China office. We have been having trouble with the ...
0
votes
0answers
24 views

IP range connected to my server suddenly times out

I've been leasing several /24 subnets from an external source and then I had my hosting company route them to my server. I've added the IPs using a network-script file ifcfg-eth0-range1 with contents ...
0
votes
1answer
302 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
votes
1answer
569 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
votes
3answers
462 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
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2answers
22k 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
3k 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 ...