Linux default gateway delete

How to remove all default gateways

I’m running a custom built Linux machine, so not all Linux commands are available.
I execute network related commands, so I need to set a default gateway right before I run my command, then remove that gateway immediately afterward. To do that I run all my commands in one line:

/sbin/route add default gw 10.10.10.10;my command;/sbin/route del default gw 10.10.10.10; 

The problem is, for some reason I once found 2 default gateways on the same machine which caused all my commands to fail because even if I set my default gateway before running my test, it is still messed up and can’t run my test. So is there a way to remove ALL default gateways in one command ? I have a large amount of machines that are increasing and it won’t be practical to plant a script on every machine. I need a command as simple as the following:

/sbin/route del all default;set my default gw;mycommand;/sbin/route del all default; 

All I have found so far is a command to remove a default gateway but not all of them /sbin/route del default which won’t work for me. /sbin/route help displays the following

/sbin/route --help Usage: route [] Edit the kernel's routing tables Options: -n Don't resolve names -e Display other/more information -A inet Select address family 

Источник

Add a Default Route on Linux

Any Linux user, especially a systems administrator, should have skills to make simple network configurations on a Linux system. For the system to communicate to the other computers on the internet, gateways must be set up and adjusted as needed.

What Will We Cover?

In this article, we will see how to add a default route on the Linux systems. Notably, different systems may have different configurations. However, we will focus on the Ubuntu 20.04 system.

What Is a Default Gateway?

To connect your home network to the wider internet, you need a default gateway. The function of a gateway is implied by its name; it connects a local area network to the wider internet.

All traffic that are not meant for the local area network and for which no alternate route is defined in the routing table are sent via the default gateway. Typically, a network’s default gateway is a specific router.

The wireless router serves as the “default gateway” in most home networks. It’s a way to connect to resources which are located on other networks that are far from your own. Internet navigation would be considerably more difficult without it.

Checking the Default Gateway

We can use the ip command and the route object to view the system’s configured routes. Since the list option is already the default action, we don’t need to include it. Additionally, we can use “r” in place of route to cut down on typing:

We can see the term “default” included in one of the routes. This is the standard route for the default gateway/route.

Automatic route addition and deletion are possible in certain cases. For example, while establishing a VPN connection, the ip r command on the same system yields a different set of results. In doing so, the network traffic is routed via a private tunnel:

With grep, it’s possible to easily isolate the default route from a large collection of configured ones:

Deleting the Default Gateway

Now, we delete the route that sends the traffic via the system’s default gateway. For this, we use the route object with the ip command and specify the delete option. Also, we require the sudo access to the routing table in order to make any modifications. First, we list the routes before deleting the default one. Then, we verify our action by listing them again:

As we can see, the default gateway entry is deleted.

Creating a New Default Gateway

The route object with an add argument can be used to create a new default gateway. Let’s take example the adding of 192.168.117.161 as the new default gateway on the wlo1 interface:

The traffic now routes via this new default gateway on enp0s3.

Making the Routing Changes Permanent

The modifications we made have immediate effect, but they are lost once the machine is restarted. You must alter a few configuration files in order to make your modifications permanent.

For example, in the case of Ubuntu, the netplan command comes in handy. Here, we need to open the netplan network configuration file:

Now, add the following configuration inside it, below the line corresponding to the renderer:

You can refer to the following screenshot. Keep in mind that the successive level of indentation is important here as well.

After saving the file, apply the changes:

Getting back to the normal command line means that the configuration is successful. Also, you can use the netplan command with the try option to examine the modifications before you apply them:

This provides you time to test your settings. If everything is set properly, you can save the configuration by hitting the “Enter” key within two minutes before the command times out. In this way, your changes are applied. Otherwise, if you don’t hit the “Enter” key, the changes only remain in the configuration file. However, your network settings are not yetmodified by them.

Note: On RHEL 8 Red Hat System, we can use the nmstatectl utility to define the gateway configuration in a YAML file. Similarly, RHEL System Roles (playbook approach) can also be used to set the default gateway.

Conclusion

We learned how to configure a default route on the Linux systems with the Ubuntu 20.04 target.

If your default gateway settings are correct, you’ll be able to communicate with the rest of the internet. However, familiarity with the hostname-to-IP address resolution is still required.

About the author

Ali Imran Nagori

Ali imran is a technical writer and Linux enthusiast who loves to write about Linux system administration and related technologies. You can connect with him on LinkedIn
.

Источник

How To Add or Change Default Route or Default Gateway in Ubuntu, Linux?

Systems connected to the network will generally access to the internet. In order to access to the internet they need some network configuration like gateway or default gateway. In this tutorial we will examine how to add or change default gateway in Ubuntu, Debian, CentOS, Fedora, Mint, Kali operating systems.

List Routing Table

Routing table is used to route IP network communication. Hosts generally uses default route to send packages which will redirect them accordingly to transmit destination. We will start by listing current routing table. We will use ip route show command like below.

Our default gateway line is

default via 192.168.122.1 dev ens3

• default means this line is default gateway
• via 192.168.122.1 specifies next hop which is default gateway IP address
• dev ens3 is the interface we want use to access default gateway

Remove Existing Default Gateway

Removing default gateway is easy if we list routing table because routing table line is used with del command like below. But keep in mind if you are connecting system remotely from different network which means if you are using default route you connection will be lost.

$ ip route del default via 192.168.122.1 dev ens3

• ip route del is our key line which deletes specified default gateway
• default via 192.168.122.1 dev ens3 is the same as routing table

Add New Default Gateway

As stated previously default gateway is used to send packages in order to transmit to the destination. We can add new default gateway with the ip route add command like below.

$ ip route add default via 192.168.1.1 dev ens3

• ip route add will add provided default gateway
• default means target network is all which is default
• via 192.168.1.1 is our default gateway network address
• dev ens3 is network interface for default gateway

Check

List routing table again and ping some of remote networks will give the status of default gateway

$ ip route show default via 192.168.1.1 dev ens3 10.0.3.0/24 dev lxcbr0 proto kernel scope link src 10.0.3.1 192.168.122.0/24 dev ens3 proto kernel scope link src 192.168.122.211

How To Add or Change Default Route or Default Gateway in Ubuntu, Linux? Infografic

Источник

Oracle Linux Add route & Delete route Default Gateway

You can Change default gateway and routing settings. I will explain Oracle Linux Add route & Delete route Default Gateway in this post.

Linux Add route delete route default gateway

Add & Delete default gateway

You can add default gateway to the linux like below.

route add default gw 192.168.163.1

If you want to delete default gateway you can execute like following script.

route delete default gw 192.168.163.1 eth1

Add route & Delete route

You can add routing and gateway settings like below.

route add -net 192.168.63.0/24 gw 192.168.163.1

Or if you want to do permanent routing, you can create route file like below.

[[email protected] ~]# [[email protected] network-scripts]# cat route-eth1 192.168.63.0/24 via 192.168.163.1 dev eth1 192.168.161.0/24 via 192.168.161.1 dev eth0

If you create routing file like above then you can restart network service like below.

[[email protected] network-scripts]# service network restart

then Routing will be like below.

[[email protected] network-scripts]# route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface default 192.168.161.1 0.0.0.0 UG 0 0 0 eth0 link-local * 255.255.0.0 U 0 0 0 ibbond0 192.168.161.0 * 255.255.255.0 U 0 0 0 eth0 192.168.16.0 * 255.255.255.0 U 0 0 0 ibbond0 192.168.18.0 * 255.255.255.0 U 0 0 0 veth1 192.168.19.0 192.168.18.1 255.255.255.0 UG 0 0 0 veth1 192.168.63.0 192.168.163.1 255.255.255.0 UG 0 0 0 eth1 192.168.163.0 * 255.255.255.0 U 0 0 0 eth1

Do you want to learn Linux System Administration for Beginners, then read the following articles.

About Mehmet Salih Deveci

I am Founder of SysDBASoft IT and IT Tutorial and Certified Expert about Oracle & SQL Server database, Goldengate, Exadata Machine, Oracle Database Appliance administrator with 10+years experience.I have OCA, OCP, OCE RAC Expert Certificates I have worked 100+ Banking, Insurance, Finance, Telco and etc. clients as a Consultant, Insource or Outsource.I have done 200+ Operations in this clients such as Exadata Installation & PoC & Migration & Upgrade, Oracle & SQL Server Database Upgrade, Oracle RAC Installation, SQL Server AlwaysOn Installation, Database Migration, Disaster Recovery, Backup Restore, Performance Tuning, Periodic Healthchecks.I have done 2000+ Table replication with Goldengate or SQL Server Replication tool for DWH Databases in many clients.If you need Oracle DBA, SQL Server DBA, APPS DBA, Exadata, Goldengate, EBS Consultancy and Training you can send my email adress [email protected] .- -Oracle DBA, SQL Server DBA, APPS DBA, Exadata, Goldengate, EBS ve linux Danışmanlık ve Eğitim için [email protected] a mail atabilirsiniz.

Источник

How to add or change the default gateway in Debian

A default gateway is a node in a PC network. The node, in this case, uses an internet protocol suite that serves as the forwarding host(router) to other networks. This occurs when no other route specification matches the destination IP address of a packet.

A gateway makes it possible for devices in one network to converse with devices in another network. For instance, if a PC requests a web page, the request goes via the default gateway exiting the LAN (local area network) to reach the internet.

You can contemplate a default gateway as an immediate device between the internet and the local network. We say this because the default gateway facilitates internal data transfer to and from the internet.

Let us now look at how traffic moves via a default gateway

How traffic maneuvers via a default gateway

Ideally, all the clients on a network point to a default gateway that routes their traffic. This traffic is passed by the default gateway from the local subnet to devices on other subnets. The default/primary gateway connects a local network to the internet, albeit internal gateways for communication purposes within a local network are utilized in corporate networks.

For instance, the default gateway in a home network setting understands particular routes that must be taken to move internet requests from a PC out of the network to the next equipment that comprehends what needs to be done. From there now, the same process recurs until data reaches its destination. Note that the word default, in this case, is the primary device that is looked for when info needs to be sent via the network.

To each network that the traffic arrives at, that network’s default gateway relays info to the internet and back to the PC that requested it.

Additionally, the default gateway is also utilized to understand the request when traffic is cosigned for other interior devices and not an external device. Therefore, instead of sending the data out of the network, it pinpoints it to the correct local device connected to the same local network.

This whole process is appreciated based on the IP address that the originating device requests.

Types of Default Gateways

There are typically two default gateway types.

Источник