Multiple ip addresses on one nic linux

Multiple ip addresses on one nic linux

The concept of creating or configuring multiple IP addresses on a single network interface is called IP aliasing. IP aliasing is very useful for setting up multiple virtual sites on Apache using one single network interface with different IP addresses on a single subnet network. Creating multiple interfaces and assign IP address to it manually is a daunting task.

Also understand how we are going to create a virtual interface and assign different range of IP Address to an interface in one go. This is how we moving forward to setup three aliases to bind the following IP addresses. For each alias you must assign a number sequentially. Go into the network directory and create the files as shown below. Finally it will look similar to below. Ping each of them from different machine. If everything setup correctly, you will get a ping response from each of them.

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multiple ip addresses on one nic linux

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Click Here to receive this Complete Guide absolutely free. I am using kernel 2. How do I bind the extra IP adresses to NIC2, so I can use these in nat and filter rules, host the same services for more than one internal host etc?

Preferably there should be no binding between the host part of the IP adress on the inside and the outside - i. Regards, Henning. Use the following designations for your ethernet devices: eth eth eth You will probably need to read up on routing as well, since each of these IP addresses will probably need a different routing table. Find More Posts by moses. Thread Tools. BB code is On.Unix Commands to remember by heart date; touch; unzip; strip; finger; ifup; mount; make love; dig; gasp; yes; uptime; ifdown; file.

It is actually very simple. It should already include a definition for eth0 virtual machines will have something else than eth0. I marked in red what is different between both definitions. Now it is up and running unless you got tons of errors?

Obviously, the eth0 interface is expected to already be up. You cannot start an alias if the main interface is not running. This command lists all the interfaces, including aliases. This also applies to the firewall. In other words, you probably won't have to make any changes to your firewall Another problem you will run into is the randomness of the IP address used to send traffic from your server to the world.

In general it won't matter, unless you have processes doing things like backups that need firewall like protection and you want to make sure that only one address is used. The IP address 1. All traffic sent to that server will be forced through eth0. If you want all your traffic to go through eth0, then don't specify the destination IP as in:.

You can enter whatever route command you need to make your system work.

Create Multiple IP Addresses to One Single Network Interface

Just tweak the parameters as required for your network. The route trick is not likely to work right with Postfix. That's usually very important for other mail system to verify your PTR. You may include several IPs, such as localhost, separated by commas.

Although at this point I did not find that there was a need for anything more. For more details about all the options available in the interface file, check out the man page of the same name:. A site for solving at least some of your technical problems Main Menu Home Search Pronounce it right! The Fox Trot story of Bill Amend. How do you do that on a Debian or Ubuntu server? The loopback network interface auto lo iface lo inet loopback The primary network interface auto eth0 iface eth0 inet static address Once you write that file to disk, you can start that interface with the ifup command: ifup eth Now it is up and running unless you got tons of errors?

To verify that the new interface is up and running, use the ifconfig command as in: ifconfig This command lists all the interfaces, including aliases. But outbound traffic comes from the wrong IP address now! In that case, you want to add a new route. On the command line, it looks like this: route add -host 1. If you want all your traffic to go through eth0, then don't specify the destination IP as in: route dev eth0 This uses 0.

To keep the route permanent i. Somehow now Postfix is using the wrong IP address The route trick is not likely to work right with Postfix. The settings go in main. More information For more details about all the options available in the interface file, check out the man page of the same name: man interfaces 1. If you want a highly secure setup, you want to have two NICs. Add new comment.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Here, I am not able to ping both IP at a time. Only one is working. Even, "ifconfig" is showing expected output.

For full explaination please follow this link:. I am writing sample configs here with You've set them up on a different subnets. So you have to setup routing to route between the different networks. Learn more.

multiple ip addresses on one nic linux

Asked 7 years, 2 months ago. Active 6 years ago. Viewed 13k times. Sorry, I wrote wrong scenario.

multiple ip addresses on one nic linux

I am using same gateway. But only one IP is working at a time. If I do ifdown to working one, second starts working. That will not work to have both on the same subnet. Only one device on a subnet can have a specific MAC address. Also, you have the same UUID but I'm not sure if that's critical to functionality - you should probably fix that, though, too Active Oldest Votes. Muneeb Ahmed Muneeb Ahmed 56 3 3 bronze badges.

multiple ip addresses on one nic linux

Check your netstat -nr to see what your routing table looks like.One of the major benefits is that you don't need a physical adapter for each IP but instead can create many virtual ones tied to a single physical card.

If you want to bind three IP's to the same NIC you would create a ifcfg-eth0 file for each alias Begin by copying the ifcfg-eth0 file:. You can verify your IP's and alias settings my issuing ifconfig. You can also test the alias connections by using ping from another system and checking for a response. You can now bind http, ftp, smtp, or nfs to different IP's if you'd like.

I tried this on CentOS 6. Home Networking General Networking How-tos. General Networking General Linux. Last Updated: Jan 17, 1 Minute Read. Reply 4. Facebook Twitter Reddit LinkedIn. GwenA 21 years in IT. Track Progress. Earn Credits. Begin by copying the ifcfg-eth0 file: cp ifcfg-eth0 ifcfg-eth cp ifcfg-eth0 ifcfg-eth Step 2: Define the settings for each alias.

Step 3: service network restart. Restart the network services to make the changes to go into effect. Spyros Christodoulou Dec 30, at am. Thank you very much, i am going to try that on my OpenSuse installation.A Linux machine -or virtual machine- can require having multiple ethernet cards, each on a separate LAN.

One reason for this can be to separate network traffic; for example, all management traffic can be routed to one NIC, while the another NIC handles all other traffic. With one single NIC, the default Linux installation will automatically set it up as a static or dynamic IP address, and a default gateway.

When there are multiple NICs, gateway routing becomes an issue.

Assign Multiple IP Addresses (Aliases) to a Single NIC

If there is incoming traffic on the other NIC, the answer is not sent back via the same route, being then effectively lost. This page explains correctly the problem happening when using multiple NICs. For this example, let's assume just two NICs, eth0 and eth1.

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It could be, instead: 1 eth0table 2 eth1table Now, it is needed to setup the routes. For the interface eth0we have:.

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Finally, it is important to note that in this file, only eth1 defines a gateway. First, let's assume that NetworkManager is not used.

Assign Multiple IP Addresses To One Interface On Ubuntu 15.10

If used, the first step is to disable it:. For eth0, the files of interest are:. Assuming now that this interface is setup dynamically using DHCP, the file ifcfg-eth0 could look like:. That is, we define the route to subnet The file rule-eth0 just defines the conditions to use this route table: from However, this is the dynamic IP address, makes no sense dumping here the received IP, which can eventually change. There is no need in this case to have the files route-eth0 or rule-eth0. But the files for eth1 are definitely required.

These files can look very similar. In the case of ifcfg-eth1 two details are important:. For the interface eth0we have: up ip route add Furthermore, this route is define in the table eth0 up ip route add default via Traffic from this interface's address Traffic to this interface's address The file route-eth0using the ip syntax, would look like: By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Server Fault is a question and answer site for system and network administrators. It only takes a minute to sign up. You'll also want to specify your routes that use that IP address using ip route. Again, the guide comes through. Even though the syntax of the ip commands makes it seem that you are associating the IP address with a specific network card, linux considers the IP address as belonging to the overall system.

Thus in some circumstances you may want to twiddle with ARP settings.

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A single network card can do this in a couple of ways; it can answer for multiple IP addresses with a single MAC address assigning multiple addresses to a NIC in most operating systems will do thisor with multiple MAC addresses virtualization platforms behave in this way.

Not only is this possible, it is very common. A network card may have multiple IP addresses. This is a concept called multihoming. There are other variants of multihoming as well.

A single physical network card definitely can have multiple IP addresses. This is almost essential when implementing server virtualization: with multiple virtual servers running on the same physical hardware, each needs its own IP address.

Setting this up is different in each Operating System, but may involve creating a new Network Interface. This can look like a unique connection but will be using the same Network Card behind the scenes. OS X and Linux use this method.

To add a new IP address in Windows open up the network connection you wish to add another IP address to. This can be used to expose a server in two network ranges. For example one network range may be used for secure traffic which the other network range cannot access. Firewall rules could be different for each Network Interface. IP layer the ip address is completely independent from the physical layer your network adapter. If your operating system has properly implemented the OSI stack or some close model of it you should be able to easily define several incoming IP addresses on a single network interface.

Handling incoming traffic over multiple IP's is pretty easy within linux. However, it's a little more tricky making outgoing traffic have different source IPs when sharing a single interface. Applications typically default to use the primary IP for outgoing source if you don't do anything special to force another IP to show up, but it's definitely possible to do this as well.


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