Programming :: Delete The Default Gateway Via NETLINK Kernel API?

Apr 15, 2010

I am looking for a way to delete the systems default gateway from the routing table via the NETLINK API.Unfortunately, the documentation I found about NETLINK is incomplete.There are some basics (communicating with the kernel, reading the routing table) but not much more.Does anyone know the packet format for deleting a routing table entry, especially deleting the default gateway? I can set or change the default gateway with the following parameters (there are more, but I left out all the non-essential ones):

NL-Msg Header:
nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE;
nlmsg_type = RTM_NEWROUTE;


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Programming :: Netlink Sockets In Kernel And Ethernet Driver - Kernel Crash

Aug 31, 2010

I write the network driver. Transmission of packets in user space I do through netlink socket`s. In user space there is a handling of packets and their transmission on other device (however, it isn't important).

Problem in that any time, packets through the driver in system, and is reverse, are transferred normally. But then there comes the moment when the kernel crash. If to look in syslog it seems to me that comes deadlock. Also I think that it is related with netlink socket`s.

I can't find the information on that anywhere how correctly to use netlink socket`s in kernel space. Can at you will any a reason into the account of synchronization of sockets and the driver in kernel space?

I can give the driver code if it is necessary.

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Programming :: Access Generic Netlink From Userspace?

Jun 7, 2010

I am trying to access a generic netlink family to send messages from user-space to the kernel. I am using libnl example here [URL].. The problem is that I keep getting

error: netlink/genl/genl.h: No such file or directory
error: netlink/genl/ctrl.h: No such file or directory
You would think I have not installed libnl and libnl-devel but I have.


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Programming :: Use Generic Netlink Receive Function - Error "sendmsg(); If(recvmsg() < 0)"

Jan 2, 2010

i'am tring to use generic netlink and can't find function for blocking not busy waiting receive. I'll try to explain myself. Generic netlink receive mechanism based on callback function - when module receives something,this function invoked. But this is not so good if you need to send something and receive answer. I mean something like that :

sendmsg(); if(recvmsg() < 0) goto err; I need generic netlink recv() function, or some mechanism to implement it. I just want to stay in "recvmsg()" function until i have answer(until call_back function invoked).

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General :: Cannot Add Default Gateway

Aug 10, 2010

Getting the following error when trying to add a default gateway for eth1.

# route add default gw eth1
route: SIOCADDRT: Network is unreachable

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Red Hat :: Set Default Gateway - Which File ?

May 28, 2010

I want to set default gateway permanently. There are two files and both have keyword "gateway":


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Networking :: Can't Set Default Gateway To Different Subnet / Do That?

Feb 3, 2011

This is slackware 12. I'm trying to share my internet connection (on eth0) with a computer connected to eth1.

eth0 is, eth1 is (different subnets).

But when I try to make eth1's default gateway the same as eth0's, see the error I get code...

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Networking :: Default Gateway On Different Subnet?

Jan 8, 2010

I am in a big confusion and searching an answer to calm down my mind.I have my eth0 has following configuration

` ` `


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General :: Unable To Add Default Gateway And DNS

Jun 18, 2010

in fedora/redhat system I want to add IP address along with Default Gateway and DNS.For assigning IP to eth0 i use the command # ifconfig etho subnet mask upthis remain temporary and when I restart my system it lost the IP address. Well to permanently add IP address in etho I use the file #cd /etc/sysconfig/network-scripts and then use # vi ifcg-eth0 to add IP address and Network Mask. How can I add Default Gateway and DNS permanently in ifcg-eth0 file or there is any other file for it ?

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Debian :: Can't Set Default Gateway By Interfaces File / What To Do?

Jul 29, 2011

I recently switched from Ubuntu server to Debian server, and I carried over many of the same configurations. This is pretty much a fresh install.

I cannot get the default gateway to stick by using the /etc/network/interfaces. I can ping my default gateway but nothing beyond it either by name or IP. code...

I would like the default gateway to stick between reboots. Could someone point me in the right direction?

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Ubuntu Networking :: Can't Ping Default Gateway

Feb 23, 2010

I have installed ubuntu 9.04 Jaunty server from disk. I am connect to my corporate internet. I have put in my http_proxy everywhere I can find to put it. I am getting an ipaddress, gateway, broadcast,etc. My wired is connected. When I try to ping my default gateway it times out. %100 packet loss. I get the ipaddress of the gateway from the (route command).

My configurations on /etc/network/interfaces is correct(I am on another computer so I can't copy and paste) and I even tried updating the drivers for NIC card. I am using a Intel 82567LM-3. I have been working on this longer than I care to admit.

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Ubuntu Servers :: Set Default Gateway For Internet / Vpn?

Jun 28, 2010

I'm having some difficulty with a internet/vpn setup. I have 3 network adapters on the server. 1x is used to connect it to the rest of the network 1x is used to provide internet (squid,dansguardian) 1x is used to connect to the vpn router

My interfaces file looks like this:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback


The problem that I have is this: When the gateway on eth2 is set to the VPN works 100% but there is no internet. When the gateway on eth2 is set to there is internet but no VPN.

So what I want to do is, route all traffic that is supposed to go to and to eth2 and all internet traffic to eth0.

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Ubuntu :: Default Gateway For Internet Connection

Jul 11, 2009

I have installed eeebuntu NBR on my laptop and it looks great on a 17 inch widescreen. It looks so different from the usual interface that I get people ask about it and I can evangalise without being considered a boring weirdo! Anyway, I have one problem. Every time I boot I have to run the following command.
Code: sudo /sbin/route add default gateway
How do I get this to happen automatically (as it normally does)?

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Networking :: Getting Default Gateway Ip Address On Interface From ISP

May 4, 2011

Im trying to achieve the multiple uplinks/provider found on I have to get the IP addresses from my interfaces (EF1 and EF2) by using a script, but i dont know where to look at for the default gateway from each interface which got their ip address from my ISP.

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Networking :: Receiving UDP Packets - Default Gateway

Apr 11, 2010

I have a computer with two interfaces: a fixed connection (eth1) and a modem (ppp0). My goal is to receive UDP packets from both connections concurrently (using the recv() function). The problem is, that the received packets reach the application only when the default gateway is set to that interface's address. For example, if I set the default gw to be in the eth1 subnet, only packets from eth1 reach the application. Other packets are received in the interface (checked using tcpdump), but they seem to be blocked somewhere. The policy defined in iptables is "ACCEPT" for all incoming packets, with no rules at all. I would like to know how to overcome this problem, and anyway how is the default gateway related to incoming UDP?

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Networking :: Reversing Default Gateway Failover

Nov 11, 2010

I have a dual-homed Debian server running squid, but not acting as a router. Simplied network diagram is below - there are other local hops between the gateways and the Internet.

(eth0 @ <--> (Gateway1 @ <--> Internet
(eth1 @ <--> (Gateway2 @ <--> Internet

Using Gateway1 gives a very fast, but not always reliable route to the Internet. Using Gateway2 gives a slower, but more reliable route to the Internet. The server uses Gateway1 as the default gateway.

I have written a script that pings three hosts on the Internet, and if all three are down, switches the default gateway to Gateway2. This part seems to be easy, but I'd like know if there is a way of routing a ICMP/ping out eth0 to a host, with all other traffic to the host going out eth1, so I can determine if the Internet is reachable via Gateway1 again.

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Networking :: Why Accept Routes In Bgp / When Have Default Gateway From ISP?

Apr 7, 2010

I am realtively new to BGP. I use BGP in my network to advertise my /20 subnet. What i would like to know is what is the point of accepting routes from your neighbouring AS(ISP)?My ISP has given me a default gateway, and no matter what I want to reach on the internet I have to go through that default gateway, so why populate the routing table with soo many routes?also, as i understand it, there are 3 kinds of routes that you can accept, those are full routes, directly connected routes and default routes. What is the diffrence between them and again how do they affect routing since my network only has the one default gateway?

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General :: Default Gateway Does Not Allow To Get Connected To The Internet?

Jan 20, 2011

i have a leased line ( speed 2 MB ) which we use to connect to our mail server , oracle ERP etc.. we have a dhcp scope defined as with a default gateway as ( which is a cisco router ) we have a pix firewall ( ).. now the gateway passed all the request to firewall..we have an ADSL of 4 MB speed.. ip is 83.*.*.230 from ISP. i have a proxy server ( squid ) eth0 is connected to ISP (83.*.*.230).. eth1 to LAN ( ) now the problem is when i put default gateway to eth1 ie the squid connects to internet via leased line.. if i leave the default gateway field empty on eth1 , the squid connects to internet via ADSL ( which i want ) but the problem is no one on the lan cant ping the squid server ( no connectivity to internet for the whole LAN ) how can i solve this problem? PS : i want squid to connect to internet with ADSL, but if i put gateway on eth1 ie LAN squid goes through leased line which i dont want to happen

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Debian Configuration :: Default Gateway Lost After Reboot?

Jul 14, 2010

after a reboot of my Lenny system, the default gateway will lost. Then i must try "networking restart" and the gatway will be set

my interfaces looks :

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback


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General :: Make Default Gateway Permanent In CentOS?

Aug 9, 2011

I have a CentOS running. It is important to have my CentOS available when I am remotely connected to a VPN router. I tried to add a default gateway to the VPN router, but after reboot it goes away. How can i put this as permanent?

ip route add via dev eth0

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Ubuntu Networking :: DUP When Pinging Default Gateway. No Internets?

Jan 30, 2011

I had a router crap out yesterday. I'd been testing out a new one for the last few days and just reconfigured it to be the main. Took the old one down and everything in my house (Windows 7 PC, XP Files server, Ubuntu PC , windows 7 laptop, android tablet, ps3, etc) seems to be working fine whether it be hard wired or wifi. All except my ubuntu 10.04 laptop. It worked fine before the swap so I can't figure out what's going on.

I'm able to connect to the new SSID without issue but I can't resolve any external names and when I try to ping the default gate way every other packet has (DUP!) behind it. If I'm hardwired I don't get the dup! when pinging the default gateway but I still can't resolve any external names. I have provided the results of an ifconfig and the results of a ping to the default gateway below.

cooley@Quigon:~$ ping
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=2.98 ms
64 bytes from icmp_seq=1 ttl=64 time=3.04 ms (DUP!)
64 bytes from icmp_seq=2 ttl=64 time=3.50 ms
64 bytes from icmp_seq=2 ttl=64 time=5.72 ms (DUP!)
64 bytes from icmp_seq=3 ttl=64 time=8.09 ms


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Networking :: CentOS-5 Server Cannot Ping Default Gateway

Jul 2, 2010

I posted it on another forum, but could not get response,So I have this cenOS, Ubuntu and windows operating system running on virtual machines.Now I gave them manual ip address, both ubuntu and windows machines can ping the default gateway, but not the CentOS.It should forward to my cisco router address(,

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Networking :: Assign Default Gateway Via DHCP At Random

Feb 21, 2011

I'm looking for a method to assign a default gateway via dhcp randomly depending on ether the last char of the mac being odd or even, or the time the user connects. Is there a good reliable way to achieve this?

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Networking :: DHCP Server Not Providing Default Gateway

Jun 16, 2011

I have installed dhcp-server on ubuntu. And server is providing ip address to clients (Window machines) but not default-gateway but I have another network in my network and same configuration and same dhcp-server provides every information.

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OpenSUSE Network :: Dropping Connection - Ignoring Default Gateway

Nov 1, 2010

I recently upgraded a 11.0 installation running on Xen Server to 11.3. I am experiencing frequent network disconnections now. The ip address and default gateway is assigned statically. However, the system seems to ignore the default gateway after a while. Then after several minutes it seems like it comes back.

root@poe5e:~/ > route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface * U 0 0 0 eth1 * U 0 0 0 eth0
link-local * U 0 0 0 eth0
loopback * U 0 0 0 lo
default UG 0 0 0 eth0
root@poe5e:~/ > ping
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=255 time=0.515 ms
64 bytes from icmp_seq=2 ttl=255 time=0.484 ms
64 bytes from icmp_seq=3 ttl=255 time=0.496 ms
64 bytes from icmp_seq=4 ttl=255 time=0.473 ms
--- ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 2997ms
rtt min/avg/max/mdev = 0.473/0.492/0.515/0.015 ms
root@poe5e:~/ > traceroute orl3akm1n
traceroute to orl3akm1n (, 30 hops max, 40 byte packets using UDP
1 ( 0.405 ms 0.398 ms 0.357 ms
2 * * *

When my sessions suddenly die and I have to coax it into routing correctly again.

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Ubuntu Servers :: Open Vpn Not Pushing Default Route/gateway?

Jun 25, 2010

i have setup an open vpn server and when i connect to it the client pulls an IP and but not default gateway. My goal is to route all web traffic through the VPN... My config file looks like this...


dev tun
proto tcp
port 1194
ca /etc/openvpn/easy-rsa/keys/ca.crt


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Networking :: Accept ICMP Redirects Not Originating From Default Gateway

Mar 9, 2011

Struggling to get my Linux server accept ICMP redirects not originating from default gateway. No problem to get it working if the redirects is originating from def gw.I know it's not a good solution security wise, but my network is so cluttered I'm forced to do so.

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Networking :: DNAT IPtables - Default Gateway For Return Packages

Nov 26, 2009

Client which uses an ISP with a Linux machine (Server 1) with two network cards. Eth0 with ip and gateway these ip's is not public ip's and falls unders the isp's internal range, eth1 with the internal ip range. OpenVPN listen on eth0 for incoming connections. We want to connect to Server1 from external networks. Due to different reasons the isp could not get the routing sorted and give us an public ip on his network. We had to setup another bos (Server2) with eth0 and gateway which is public ip's and eth1 with ip Server 2 can communicate via the ISP internal network with server 1. I use DNAT to forward all incoming connections on server 2 to server 1 but the problem I have is that server uses its default gateway for the return packages and does not sent the reply back to server 2. My iptables rules looks as follows on server 2.

/usr/sbin/iptables -t nat -A PREROUTING -p udp -i eth0 -d --dport 1194 -j DNAT --to
/usr/sbin/iptables -A FORWARD -p udp -i eth0 -d --dport 1194 -j ACCEPT

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Networking :: Normal Default Gateway Reappears With OpenVPN Redirect

Apr 22, 2009

I'm using OpenWRT on a WRT54GS. I'm using wifidog in combination with openvpn. For those of you familiar with wifidog, my auth server is located at the other end of an openvpn tunnel and the "wifi dog gateway" is running on the WRT itself. I'm don't really think that wifi dog is the issue. Basically, I'm using openvpn with the "redirect-gateway" option which works well. In this mode, openvpn removes my current default gateway setting and adds the remote openvpn server as the default gateway (as it should). However, overnight, my default gateway on the local network keeps reapperaing (along with the openvpn one as well).

This causes confusion and I don't want any packets (But ovbiously the connection to the actual openvpn server) to go down this local gateway. Why do you think it reappears? Do you reckon openvpn is dropping connection and somehow the normal gateway is being added back? I *could* run a cron script which runs every minute or so with something like "route del default gw xx.xx.xx.xx" (where xx.xx.xx.xx is the default gateway which I don't want to be there) but that is quite messy and means that if I were to ever move the router I would need to reconfigure this and considering that I would like in the future to have many of these wifi dog gateways, this really isn't an ideal option (as every network will have a different default gateway).

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CentOS 5 Networking :: Unable To Configure Default Gateway Onto The System

Dec 19, 2010

I could not able to configure the default gateway ip address onto the system. i use the route command (" route add default gw eth0 ") to add a default gateway onto the routing table but it is "disappear" in the routing table when i had restart the service network.

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