TranslateProject/sources/tech/20220919 How To Find Default Gateway IP Address In Linux And Unix From Commandline.md

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[#]: subject: "How To Find Default Gateway IP Address In Linux And Unix From Commandline"
[#]: via: "https://ostechnix.com/find-default-gateway-linux/"
[#]: author: "sk https://ostechnix.com/author/sk/"
[#]: collector: "lkxed"
[#]: translator: " "
[#]: reviewer: " "
[#]: publisher: " "
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How To Find Default Gateway IP Address In Linux And Unix From Commandline
======
5 Ways To Find Gateway Or Router IP Address In Linux
A **gateway** is a node or a router that allows two or more hosts with different IP addresses to communicate with each other when connected to the same router. Without gateway, devices connected on the same router wont be able to communicate with each other. To put this another way, the gateway acts as an access point to pass network data from a local network to a remote network. In this guide, we will see all the possible ways to **find default gateway in Linux** and **Unix** from commandline.
#### Contents
1. Find Default Gateway In Linux 2. 1. Find Default Gateway Using ip Command 3. 2. Display Default Gateway IP Address Using route Command 4. 3. View Gateway IP Address Using netstat Command 5. 4. Print Default Gateway IP Address Or Router IP Address Using routel Command 6. 5. Find Gateway From Ethernet Configuration Files
7. Conclusion
### Find Default Gateway In Linux
There are various commandline tools are available to view the gateway IP address in Linux. The most commonly used tools are: **ip**, **ss**, and **netcat**. We will see how check the default gateway using each tool with examples.
#### 1. Find Default Gateway Using ip Command
The **ip** command is used to show and manipulate routing, network devices, interfaces and tunnels in Linux.
To find the default gateway or Router IP address, simply run:
```
$ ip route
```
Or,
```
$ ip r
```
Or,
```
$ ip route show
```
**Sample output:**
```
default via 192.168.1.101 dev eth0 proto static metric 100
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.20 metric 100
```
Did you see the line **"default via 192.168.1.101"** in the above output? This is the default gateway. So my default gateway is **192.168.1.101**.
You can use **-4** with `ip route` command to **display the IPv4 gateway** only:
```
$ ip -4 route
```
And, use `-6` to **display the IPv6 gateway** only:
```
$ ip -6 route
```
As you noticed in the output, the IP address and the subnet details are also shown. If you want to display ONLY the default gateway and exclude all other details from the output, you can use `awk` command with `ip route` like below.
To find the default gateway IP address using `ip route` and `grep`, run:
To print Gateway IP address with `ip route` and `awk` commands, run:
```
$ ip route | awk '/^default/{print $3}'
```
Or,
```
$ ip route show default | awk '{print $3}'
```
This will list only the gateway.
**Sample output:**
```
192.168.1.101
```
![Find Default Gateway Using ip Command][1]
You can also use **[grep][2]** command with `ip route` to filter the default gateway.
```
$ ip route | grep default
default via 192.168.1.101 dev eth0 proto static metric 100
```
The `ip route` is the recommended command to find the default gateway IP address in latest Linux distributions. However, some of you may still be using the legacy tools like **route** and `netstat`. Old habits die hard, right? The following sections explains how to determine the gateway in Linux using `route` and `netstat` commands.
#### 2. Display Default Gateway IP Address Using route Command
The **route** command is used to show and manipulate routing table in older Linux distributions, for example RHEL 6, CentOS 6.
If you're using those older Linux distributions, you can use the `route` command to display the default gateway.
Please note that the `route` tool is deprecated and replaced with `ip route` command in the latest Linux distributions. If you still want to use `route` for any reason, you need to install it.
First, we need to check which package provides `route` command. To do so, run the following command on your RHEL-based system:
```
$ dnf provides route
```
**Sample output:**
```
net-tools-2.0-0.52.20160912git.el8.x86_64 : Basic networking tools
Repo : @System
Matched from:
Filename : /usr/sbin/route
net-tools-2.0-0.52.20160912git.el8.x86_64 : Basic networking tools
Repo : baseos
Matched from:
Filename : /usr/sbin/route
```
As you can see in the above output, the net-tools package provides the `route` command. So, let us install it using command:
```
$ sudo dnf install net-tools
```
Now, run `route` command with `-n` flag to display the gateway IP address or router IP address in your Linux system:
```
$ route -n
```
**Sample output:**
```
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.1.101 0.0.0.0 UG 100 0 0 eth0
172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
192.168.1.0 0.0.0.0 255.255.255.0 U 100 0 0 eth0
```
![Display Default Gateway IP Address Using route Command][3]
As you see in the above output, the gateway IP address is 192.168.1.101. You will also see the two letters **"UG"** under Flags section. The letter **"U"** indicates the interface is **UP** and **G** stands for Gateway.
#### 3. View Gateway IP Address Using netstat Command
**Netstat** prints information about the Linux networking subsystem. Using netstat tool, we can print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships in Linux and Unix systems.
Netstat is part of net-tools package, so make sure you've installed it in your Linux system. The following commands install net-tools package in RHEL-based systems:
```
$ sudo dnf install net-tools
```
To print the default gateway IP address using `netstat` command, run:
```
$ netstat -rn
```
**Sample output:**
```
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.1.101 0.0.0.0 UG 0 0 0 eth0
172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
```
![View Gateway IP Address Using netstat Command][4]
The `netstat` command's output is same as `route` command's output. As per the above output, the gateway IP address is 192.168.1.101 and the UG stands the NIC associated to gateway is UP and G indicates Gateway,
Please note that `netstat` is also deprecated and it is recommended to use **"ss"** command instead of netstat.
#### 4. Print Default Gateway IP Address Or Router IP Address Using routel Command
The **routel** is a script to list routes with pretty output format. The routel script will list routes in a format that some might consider easier to interpret then the `ip route` list equivalent.
The routel script is also the part of net-tools package.
To print the default gateway or router IP address, run routel script without any flags like below:
```
$ routel
```
**Sample output:**
```
target gateway source proto scope dev tbl
default 192.168.1.101 static eth0
172.17.0.0/ 16 172.17.0.1 kernel linkdocker0
192.168.1.0/ 24 192.168.1.20 kernel link eth0
127.0.0.0/ 8 local 127.0.0.1 kernel host lo local
127.0.0.1 local 127.0.0.1 kernel host lo local
127.255.255.255 broadcast 127.0.0.1 kernel link lo local
172.17.0.1 local 172.17.0.1 kernel hostdocker0 local
172.17.255.255 broadcast 172.17.0.1 kernel linkdocker0 local
192.168.1.20 local 192.168.1.20 kernel host eth0 local
192.168.1.255 broadcast 192.168.1.20 kernel link eth0 local
::1 kernel lo
::/ 96 unreachable lo
::ffff:0.0.0.0/ 96 unreachable lo
2002:a00::/ 24 unreachable lo
2002:7f00::/ 24 unreachable lo
2002:a9fe::/ 32 unreachable lo
2002:ac10::/ 28 unreachable lo
2002:c0a8::/ 32 unreachable lo
2002:e000::/ 19 unreachable lo
3ffe:ffff::/ 32 unreachable lo
fe80::/ 64 kernel eth0
::1 local kernel lo local
fe80::d085:cff:fec7:c1c3 local kernel eth0 local
```
![Print Default Gateway IP Address Or Router IP Address Using routel Command][5]
To print only the default gateway, run routel with `grep` like below:
```
$ routel | grep default
default 192.168.1.101 static eth0
```
#### 5. Find Gateway From Ethernet Configuration Files
If you have **[configured static IP address in your Linux or Unix][6]** system, you can view the default gateway or router IP address by looking at the network configuration files.
In RPM-based systems like Fedora, RHEL, CentOS, AlmaLinux and Rocky Linux, the network interface card (shortly **NIC**) configuration are stored under **/etc/sysconfig/network-scripts/** directory.
Find the name of the network card:
```
# ip link show
```
**Sample output:**
```
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0@if5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
link/ether d2:85:0c:c7:c1:c3 brd ff:ff:ff:ff:ff:ff link-netnsid 0
```
The network card name is **eth0**. So let us open the network card configuration of this NIC card file:
```
# cat /etc/sysconfig/network-scripts/ifcfg-eth0
```
**Sample output:**
```
DEVICE=eth0
ONBOOT=yes
UUID=eb6b6a7c-37f5-11ed-a59a-a0e70bdf3dfb
BOOTPROTO=none
IPADDR=192.168.1.20
NETMASK=255.255.255.0
GATEWAY=192.168.1.101
DNS1=8.8.8.8
```
As you see above, the gateway IP is `192.168.1.101`.
In Debian, Ubuntu and its derivatives, all network configuration files are stored under **/etc/network/** directory.
```
$ cat /etc/network/interfaces
```
**Sample output:**
```
auto ens18
iface ens18 inet static
address 192.168.1.150
netmask 255.255.255.0
gateway 192.168.1.101
dns-nameservers 8.8.8.8
```
Please note that this method should work only if the IP address is configured manually. For DHCP-enabled network, you need to follow the previous 4 methods.
### Conclusion
In this guide, we listed 5 different ways to find default gateway in Linux and Unix operating systems. We also have included sample commands to display the gateway/router IP address in each method. Hope this helps.
--------------------------------------------------------------------------------
via: https://ostechnix.com/find-default-gateway-linux/
作者:[sk][a]
选题:[lkxed][b]
译者:[译者ID](https://github.com/译者ID)
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[a]: https://ostechnix.com/author/sk/
[b]: https://github.com/lkxed
[1]: https://ostechnix.com/wp-content/uploads/2022/09/Find-Default-Gateway-Using-ip-Command.png
[2]: https://ostechnix.com/the-grep-command-tutorial-with-examples-for-beginners/
[3]: https://ostechnix.com/wp-content/uploads/2022/09/Display-Default-Gateway-IP-Address-Using-route-Command.png
[4]: https://ostechnix.com/wp-content/uploads/2022/09/View-Gateway-IP-Address-Using-netstat-Command.png
[5]: https://ostechnix.com/wp-content/uploads/2022/09/Print-Default-Gateway-IP-Address-Or-Router-IP-Address-Using-routel-Command.png
[6]: https://ostechnix.com/configure-static-ip-address-linux-unix/