Linux – Virtual IP not getting pinged: wrong settings

iplinuxnetworkingrouting

I am working on Linux.

I added a route to a virtual IP say: 100.10.10.2 by running the command:

route -n add 100.10.10.2 gw 127.0.0.1

It has been redirected to my local loopback. I checked the kernel IP table and it has the path setup correctly. Now, I run a script that binds on the same IP and then try to ping the IP from my machine, it gets the ping reply correctly.

But another computer on the same network cannot ping this virtual IP address. I checked up on the Internet and it does say that I can have multiple IPs on my local loopback and they can be viewed from the peers on the same network.

I tried adding a path on the eth0 interface by replacing the 127.0.0.1 by my eth0 IP address. The information was added to the route table correctly, but then the same thing happened: I was able to ping from my own machine but the peer couldn't.

I Googled up the same thing but none of the solutions helped me out.

The script (it send back ICMP packet replies) is correct (I am sure of that) since I get ping replies from my own machine for the IP which I set up the route for.

Where am I going wrong? Or am I missing out on some configuration?

Any help is much appreciated!

EDIT:

This is the route table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
100.10.10.2     localhost.local 255.255.255.255 UGH   0      0        0 lo
192.168.1.0     *               255.255.255.0   U     1      0        0 eth0
link-local      *               255.255.0.0     U     1000   0        0 eth0
default         192.168.1.1     0.0.0.0         UG    0      0        0 eth0

and interface config:

eth0     Link encap:Ethernet  HWaddr 00:22:19:ec:ee:50  
          inet addr:192.168.1.2  Bcast:10.200.200.255  Mask:255.255.255.0
          inet6 addr: fe80::222:19ff:feec:ee50/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1

Best Answer

I am unclear why you're mucking about with route commands on the local system in any case. If you have an address configured on one of your local interfaces, you don't need to specify an explicit route; your system will already know how to contact it.

So for example, if you already have eth0 configured as above, you should be able to do this:

ifconfig eth0:0 100.10.10.2 netmask 255.255.255.0

And now your local system will be all set.

For other systems on your network to contact your system at that ip address, one of three things will need to be true. Either:

  • they need to have an interface on the same ip network, or
  • they need to have an explicit route to that ip network, or
  • their default gateway needs to have a route to that ip network

So if you have another system with the "real" address is 192.168.1.3, then you would either do this:

ifconfig eth0:0 100.10.10.3 netmask 255.255.255.0

Or this:

route add -net 100.10.10.0/24 dev eth0
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