Santhosh,
While I haven't seen the same message that you are seeing i.e. "Reply not for us" there is definately a bug in the SDK 7.0 kernel (kernel 3.12.10) with and the cpsw that affects DHCP and it doesn't seem to be consistent across boards.
See this thread:
http://e2e.ti.com/support/arm/sitara_arm/f/791/t/338842.aspx
And this this:
http://e2e.ti.com/support/arm/sitara_arm/f/791/p/333389/1163824.aspx#1163824
With my AM335x-EVMSK board and stock SDK 7.0 I can not get ethernet to work at all, whether I'm using DHCP or not and like you it works with SDK 6.
It's been a while now but I think that moving to a newer kernel with the suggested fix solved the problem but can't be certain, it's been on my to do list to test this again.
On another note, my BeagleBone Black seems to work fine with stock SDK 7.0 so go figure.
I've asked a couple of times when a patch is going to be issued for the SDK and gotten no response.
I hope this helps.
Matt S.