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Currently I'm running a FreeBSD 9.1 and the default gateway is already configured in the rc.conf.

rc.conf:

defaultrouter = "10.0.0.1"

But now I want to change the default gateway without rebooting the system, is this possible?

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migrated from serverfault.com Aug 21 '13 at 2:02

This question came from our site for system and network administrators.

7 Answers 7

up vote 8 down vote accepted
route del default
route add default 1.2.3.4

Where 1.2.3.4 is the new gateway. You can even concatenate them onto the same line with a ;

Edit: This is FreeBSD, not Linux. The command is different. Please do not edit this Answer if you haven't read the Question carefully enough to determine the operating system being used.

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+1 for the semi-colon trick ;) –  msw Aug 21 '13 at 3:55
1  
Note: do this in console, not over ssh. If you must do this via ssh (or other network method), issue both commands at once, with ; or with && –  Dalibor Filus Jul 8 '14 at 14:58
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Or, use the generic safe method: 1) Log into a shell, shutdown/reboot in 15 minutes unless cancelled 2) Do unsafe things. 3) Cancel shutdown/reboot. –  Hennes Jul 8 at 17:24

yes just change the route and restart your network.

/etc/rc.d/netif restart
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1  
That works, though it restarts a heck of a lot... and might break applications that are bound to interfaces. –  Chris S Aug 21 '13 at 1:59

You can add a new default route and remove the old one using either the ip or route command. The above commands will replace the gateway with 192.0.2.1. Both command pairs do the same thing. FreeBSD and other OSs should have one or both programs, possibly with slightly different formats. (FreeBSD has the route command and excludes the gw keyword used in other implementations.) The commands man ip and/or man route should provide you with documentation on your specific implementation.

route add default 192.0.2.1
route del default 10.0.0.1

ip route add default via 192.0.2.1
ip route del default via 10.0.0.1 

There are multiple implementations of these commands, so the above may not match your implementation. Your implementation should have a man page with examples for common use cases such as adding and removing default gateways. Try man route and man ip to see how your implementation works.

Change 192.0.2.1 to your desired default gateway. The default gateway needs to be on one of networks you have a direct connection to. You can change your IP address in a similar manner. ip is a newer tool which will do most everything you need to do to view and manage IP addresses and routing on IPv4 and IPv6 networks. ifconfig is an an older tool for configuring IP addresses on an IPv4 network.

To make the change permanent, update your network configuration files in /etc. The file(s) vary depending on the distribution you are using.

At least one of these commands should be available on any Unix derived O/S. Different versions may work slightly differently. Check the man page for details on your O/S.

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4  
-1 Sorry, but these are Linux commands and don't work on FreeBSD. –  Chris S Aug 21 '13 at 1:59
    
@ChrisS updated to reference the changes for FreeBSD. route has multiple implementations with minor syntax changes. –  BillThor Jul 9 at 4:31

It's very easy, you only need to type the next commands:

$ route del 0/0
$ route add 0/0 192.168.0.1

You gonna need to replace the '192.168.0.1' with the IP of your choice.

And to check the changes you can use 'netstat':

$ netstat -r

This command show the routing table of the system.

Hope this help you.

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What is "0/0" ? –  WWW Aug 21 '13 at 15:20
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@WWW '0/0' is the abbreviation of the network block '0.0.0.0/0', which is the same as 'default', but I prefer '0/0' (I suppose i'm more of the old school). –  ifm Aug 21 '13 at 17:23

Here's a one-liner:

ip route replace default via 1.2.3.4

Where 1.2.3.4 is the new gateway IP

credit

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-1 Sorry, but these are Linux commands and don't work on FreeBSD. –  Chris S May 22 at 15:49

Always first use netstat -nr to check the gateway what you have and what the details it has...you See 0.0.0.0. when its a default one and you should first think that why am I changing this gateway than use this command:

route add default gw your ip eth0
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-1 Sorry, but these are Linux commands and don't work on FreeBSD. –  Chris S Jul 9 at 19:10

You could try:

route add default gw 192.168.1.254 eth0
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-1 Sorry, but these are Linux commands and don't work on FreeBSD. –  Chris S May 22 at 15:49
    
Route add is part of my FreeBSD 8.4 install though. But yeah, many people here who answer for the wrong OS. –  Hennes Jul 8 at 17:26
    
@Hennes the route add part works fine. GNU/Linux added the gw part, which doesn't work on any other *nix. Without the gw works on all the BSDs, Solaris, OSX, HPUX, AIX, etc. –  Chris S Jul 9 at 19:10

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