Detect NIC Interface In Linux

Hi

We are going to move some servers from one location to another. How to verify whether the cables are connected to the right interface port?

like one server has eth0 active and eth1 is down. now if the tech guys connect the cable on eth1 port then how to know that

Is it /sys/class/net/eth1 and look for carrier or there is a better way ?

thanks in advance

Hi,

I tried to configure my ethernet interface on a Debian Wheezy VM, but I've a problem. When I try to restart /etc/init.d/networking, I've no error message.
But my eth1 interface isn't up and when I try to up it with : ifup eth1, it return me :

Code:

root@debian-main:/# ifup eth1
RTNETLINK answers: File exists
Failed to bring up eth1

My /etc/network/interface file is :

Code:

auto eth0
allow-hotplug eth0
iface eth0 inet dhcp


iface eth1 inet static
        address 192.168.10.1
        netmask 255.255.255.0
        gateway 192.168.10.254

Eth0 is my internet interface and eth1 is a local interface. I want to install a DNS and a DHCP server on eth1 to be able to connect client with this VM and give them an ip adress.

Thanks guys

Hello, I have an expect script where I ssh to a remote host to determine the network configuration and get from the user the network interface card that should be used. From their response, I determine the subnet mask and save the information to a text file that is later transmitted back to my local host. This is all so that I can set up virtual IP aliasing and verify that the physical IP address of the local and remote host are on the same subnet prior to continuing with the setup. I am running the script on Linux, with expect version 5.45.

The code itelf works just fine, but I'm having some issues with how it displays on the screen. As you'll see below in the example, the default system prompt displays, as does the user input command that I'm sending to the shell from the expect script.

Is there a regular expression or something that I can write to prevent the prompt and command that I'm sending from printing to the screen? I know that it should be suppressed if I have an expect command following the Code:

send -s "\nread n_card?'Enter the network interface card number for this server (i.e. eth0):   '\r

command, but everything I have tried for strings and regular expressions to expect causes the netstat -rn output to not show up all of a sudden. I'm new to expect, so I'm not really sure why this is happening.

I would really appreciate any help/suggestions. Thanks for your time!

Part of the Script Code:
Code:

expect {
   -re $prompt {   ;# Send individual commands and get user input
        set timeout -1
        
        # Get partner hostname and put in vipsetup.txt file
        send -s "hostname > vipsetup.txt\r"  
        expect -re $prompt
        
        # Display the network routing info for the user and prompt for 
        # network interface card number
        send -s "print \"The network routing table for the $ptner server is displayed below:\n\" ; netstat -rn \r"
        
        expect -re "\r(.*):\r"
        send -s "\nread n_card?'Enter the network interface card number for this server (i.e. eth0):   '\r"
        interact "\r" return    ;# Wait for user input from read command
        send -- "\r"
        send -s "echo \$n_card >> vipsetup.txt\r"  
        
        # Obtain subnet mask information for partner based on network 
        # interface card number being used
        send -s "msk=\$(cat /etc/sysconfig/network-scripts/ifcfg-\$n_card | grep NETMASK)\r"
        send -s "msk=\$(echo \${msk#NETMASK=})\r"
        send -s "echo \$msk >> vipsetup.txt\r"
    }
    timeout {
        send_user "Connection to host $hostip timed out."
        exit 6 
    }
    eof {
        send_user "Connection to host $hostip failed."
        exit
    }
}

Script Output:
Code:

The network routing table for the PRIMARY server is displayed below:
 
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.105.65.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
0.0.0.0         10.105.65.1     0.0.0.0         UG        0 0          0 eth0
 [root@remotehost root]$
[root@remotehost root]$ ber for this server (i.e. eth0):   '              < 
Enter the network interface card number for this server (i.e. eth0):   eth0

Hello, My issue is very common but, not able to resolve it.

Issue I am facing with my Linux (RHEL-5 32-bit) machine, where I am not able to connect to internet.

DWR-113 - D-Link Router is configured for 3G dongle (Vodafone India) - This setup is done via WiFi and not using the provided LAN cable from Win7 machine.

Internet is working absolutely fine in case of Wireless but, at same time when LAN cable is used internet is not working. [Able to ping to Router IP i.e. 192.168.0.1)

Similarly, from Linux box, ping to Router IP is working [LAN plugged] but, Internet not working. IP of linux machine: 192.168.0.60

Also, able to get the console connection of Linux from Windows box..[Windows connected to Router via WiFi and Linux connected to Router via LAN cable]

Please suggest how to get rid of this problem so that Internet will work on Linux via LAN cable.

Many Thanks,

Java Application that we are currently using, read the IP information via using sigar library(sigar.getNetInterfaceConfig()

when we use the sigar.getNetInterfaceConfig(), it brings Primary Network Interface from the

server, and this is the problem for us.

we are using Centos server now and connected with 2 of network which are eth0, eth1.

we need to gather the IP from etho0, however in sigar, it brings the ip from eth1.

It seems that primary IP of current server set as eth1.

Therefore, we were looking for answer to modify primary IP at Centos, but could not find yet.

We really want to know how to modify or set up primary IP at Centos.

Thanks for reading such a long story from us.

Regards,

Kihong, Ko

ps. i used CentOS6

Hi all

I got this interesting problem:

I have a server that has two ethernet connections, cabled up to the switch.

The server has a clonezilla liveboot cd in it which I am currently booting from. The clonezilla is a debian OS.

So from the cmd line I can see I have two eth interfaces that is connected, eth0 and 2.

Now I need to configure one of these two interfaces to do let clonezilla do its job.

The problem is that each of these two interfaces are going to different subnets. I got the two subnets, which we will just call them A and B. And I can't recall whether A belongs on eth0 or B belongs there.

Now I know there is a simple solution to this: config one and try it out. I could do that, in fact I will do that just to save time. But I was wondering, cause when I did ifconfig I can see from the packet counters that these two interfaces are live, if there is some other way to monitor these two interfaces, and by looking at the packets that is being sent to these interfaces, I can determine which interface goes with which subnet?

Or phrased another way: you just installed a new computer, and have plugged in the internet cable, but you forgot to put an IP address on it and really don't want to wait for your IT guy to come in on monday to tell you what your IP is and dhcp is not an option. What do you do?

Thanks
Feel free to ask questions if anything is not clear.

Hi all,

I have a host#1 with ip=192.168.3.100 and a host#2 with ip=192.168.2.100. Both hosts are connected to some linux device with 2 interfaces : eth0 with ip=192.168.2.1 and eth1 with ip=192.168.3.1.

So host#1 is connected to eth1 and host#2 to eth0. I would like to ping host#2 from host#1 and vice versa. How can I do that ?

I tried :
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT
iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

but it didn't work

PS
This is my first post here, so please don't be very strict to me
Looking forward to hearing from anybody as I'm out of ideas...

BR,
Dmitry

Hi all

I am trying out this dhcp server setup on opensuse 12.1 but it does not seem to be working.

I have eth0 configured to be 192.168.10.1 in a /24 network.

I want to hand out the rest of the address in the same subnet as dhcp addresses. (So everything from 10.2 to 10.255). The default gw is defined as 192.168.10.1, and routing table looks correct. and I only have eth0.


When I start the dhcp, and connect it to the client machine, I see nothing on the wireshark trace. no DHCP discovery or ack messages. And the client machine just keeps trying boot from the network via the network interface. I know I got the right interface (there were blinky options in the bios that lets you identify the correct interface) and the cable is not a problem. (If the cable were a problem the client boot message would say "media fault ... please check media...") instead.

Here is my dhcpd.conf file. I went through man dhcpd already, and cleaned out everything that I apparently don't need. (The original file was copied from a more complicated setup that had multiple subnets and dhcp relays.)

Code:

###################simplfied 
linux-kzy1:/var/lib/dhcp/db # cat /etc/dhcpd.conf
authoritative;

ddns-update-style none;
ddns-updates off;

#Information about the host
subnet 192.168.10.0 netmask 255.255.255.0 {
  max-lease-time 600;
  default-lease-time 600;
  range 192.168.10.2 192.168.10.255;
}

group esx_gep{
  filename "pxelinux.0";
  next-server 192.168.10.1; 
  host testserver1 {hardware ethernet a0:d3:c1:f7:f2:64;}
}

this is what /var/log/message and /var/log/rc.dhcpd.log says:
Code:

**************var log message
Mar 19 18:42:17 linux-kzy1 dhcpd: For info, please visit https://www.isc.org/software/dhcp/
Mar 19 18:42:17 linux-kzy1 dhcpd: Not searching LDAP since ldap-server, ldap-port and ldap-base-dn were not specified in the config file
Mar 19 18:42:17 linux-kzy1 dhcpd: Wrote 0 group decls to leases file.
Mar 19 18:42:17 linux-kzy1 dhcpd: Wrote 0 deleted host decls to leases file.
Mar 19 18:42:17 linux-kzy1 dhcpd: Wrote 0 new dynamic host decls to leases file.
Mar 19 18:42:17 linux-kzy1 dhcpd: Wrote 0 leases to leases file.
Mar 19 18:42:17 linux-kzy1 dhcpd: Listening on LPF/eth0/84:8f:69:cf:7c:41/192.168.10.0/24
Mar 19 18:42:17 linux-kzy1 dhcpd: Sending on   LPF/eth0/84:8f:69:cf:7c:41/192.168.10.0/24
Mar 19 18:42:17 linux-kzy1 dhcpd: Sending on   Socket/fallback/fallback-net
Mar 19 18:42:17 linux-kzy1 dhcpd[12233]: Starting ISC DHCPv4 4.x Server [chroot]..done
linux-kzy1:/home/test/Documents #


*****************var log rc.dhcpd.log
Mar 19 18:42:17 linux-kzy1 dhcpd: Internet Systems Consortium DHCP Server 4.2.2
Mar 19 18:42:17 linux-kzy1 dhcpd: Copyright 2004-2011 Internet Systems Consortium.
Mar 19 18:42:17 linux-kzy1 dhcpd: All rights reserved.
Mar 19 18:42:17 linux-kzy1 dhcpd: For info, please visit https://www.isc.org/software/dhcp/
Mar 19 18:42:17 linux-kzy1 dhcpd: Not searching LDAP since ldap-server, ldap-port and ldap-base-dn were not specified in the config file
Mar 19 18:42:17 linux-kzy1 dhcpd: Wrote 0 group decls to leases file.
Mar 19 18:42:17 linux-kzy1 dhcpd: Wrote 0 deleted host decls to leases file.
Mar 19 18:42:17 linux-kzy1 dhcpd: Wrote 0 new dynamic host decls to leases file.
Mar 19 18:42:17 linux-kzy1 dhcpd: Wrote 0 leases to leases file.
Mar 19 18:42:17 linux-kzy1 dhcpd: Listening on LPF/eth0/84:8f:69:cf:7c:41/192.168.10.0/24
Mar 19 18:42:17 linux-kzy1 dhcpd: Sending on   LPF/eth0/84:8f:69:cf:7c:41/192.168.10.0/24
Mar 19 18:42:17 linux-kzy1 dhcpd: Sending on   Socket/fallback/fallback-net
Mar 19 18:42:17 linux-kzy1 dhcpd[12233]: Starting ISC DHCPv4 4.x Server [chroot]..done
linux-kzy1:/home/test/Documents #

not very interesting stuff or useful, but I found some other messages that is very interesting:

Code:

**********
#no free lease

linux-kzy1:/home/test/Documents # cat /var/log/messages | grep "free lease"
Mar 19 15:53:59 linux-kzy1 dhcpd: DHCPDISCOVER from a0:d3:c1:f7:f2:64 via eth0: network 192.168.10.0/24: no free leases
Mar 19 15:54:03 linux-kzy1 dhcpd: DHCPDISCOVER from a0:d3:c1:f7:f2:64 via eth0: network 192.168.10.0/24: no free leases
Mar 19 15:54:11 linux-kzy1 dhcpd: DHCPDISCOVER from a0:d3:c1:f7:f2:64 via eth0: network 192.168.10.0/24: no free leases
......
Mar 19 17:01:06 linux-kzy1 dhcpd: DHCPDISCOVER from a0:d3:c1:f7:f2:64 via eth0: network 192.168.10.0/24: no free leases
Mar 19 17:01:38 linux-kzy1 dhcpd: DHCPDISCOVER from a0:d3:c1:f7:f2:64 via eth0: network 192.168.10.0/24: no free leases
linux-kzy1:/home/test/Documents #

Which ties into my first question: dhcp no free lease: I googled a bit, I found a post from a guy on ubuntu who has the same error message and the suggested course of action is to change ownership of the lease file to dhcpd and give it 777 for permission. Which I thought is weird, because the lease file is automatically created by the dhcpd itself, so it really shouldn't be a permission issue shouldn't it? (Anyway, tried that didn't do a thing.) right now it is owned by root/root and has this permission: -rw-r--r--.

2nd question: once the client gets a reply from my dhcp server saying no free lease, does it remember this dhcp server as no free lease and does it persist throughout reboots? Because I tried rebooting the client a number of times and I don't see anything on the wireshark at all. You will notice the time stamp on the last "no free lease" message is not as late as the other messages from the var/log/messages or rc.dhcpd.log and I rebooted the client and the dhcp plenty of times since 17:01:38.



Thanks for all your help in advance everyone.

I want to connect my laptop to the TV to view sports etc. but when I plug in the HDMI cable nothing happens, the program just continues on the laptop. I am using Xubuntu and am completely new to Linux


Hello guys thanks for helping. I solved the problem by going to Display in Settings and selecting "Configure new displays on connecting". This enabled the TV when I plugged in the HDMI cable. Thanks again. Liam

I am trying to set up a "Proxy Server" in Linux, without using Squid (Part of my project). However I have beginner's knowledge of iptables. I am using the following script from "http://www.aboutdebian.com/proxy.

#!/bin/sh
INTIF="eth1"
EXTIF="eth0"
EXTIP="`/sbin/ifconfig eth0 | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'`"
/sbin/depmod -a
/sbin/modprobe ip_tables
/sbin/modprobe ip_conntrack
/sbin/modprobe ip_conntrack_ftp
/sbin/modprobe ip_conntrack_irc
/sbin/modprobe iptable_nat
/sbin/modprobe ip_nat_ftp
echo "1" > /proc/sys/net/ipv4/ip_forward
echo "1" > /proc/sys/net/ipv4/ip_dynaddr
iptables -P INPUT ACCEPT
iptables -F INPUT
iptables -P OUTPUT ACCEPT
iptables -F OUTPUT
iptables -P FORWARD DROP
iptables -F FORWARD
iptables -t nat -F
iptables -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT
iptables -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE

Question is there is no packet forwarding from eth1 to eth0 (verified from wireshark, a windows is using eth1's ip address as its default gateway)

Any help would be highly appreciated!