when I connect the LAN cable in mother board it is not working but when I connected an external LAN card it was working fine . Is there any solution where I can use the on board LAN
please advice
Apparently you do not have a driver that can handle the on-board NIC. My daughter had the same problem with a machine she built a while back - the NIC on the motherboard was too new and a driver was not available and she had to install an older NIC card and use that.
You will have to determine exactly what NIC chip is used on your motherboard and search for a driver for it, or configure a driver yourself (or something like that. this is sort of out of my league).
In fact, you can check if the kernel recognizes your NIC with a lspci -k; look for "Ethernet controller". This should show you the "Kernel driver in use" and "Kernel modules" for each device.