Unable to boot via usb_ether

Hi,

I have been trying to tftp boot uImage.

Here is my setup:
BBB is connected via USB cable to host.
UBoot is configured for usb_ether.
Uboot receives IP from DHCP server and loads uImage.
The kernel starts.

However, the booting does not progress further as (I think) NFS is not getting loaded.

[ 1.553308] omap_i2c 4819c000.i2c: bus 2 rev0.11 at 100 kHz
[ 1.560933] hctosys: unable to open rtc device (rtc0)
[ 1.583001] net eth0: initializing cpsw version 1.12 (0)
[ 1.588374] net eth0: initialized cpsw ale version 1.4
[ 1.593624] net eth0: ALE Table size 1024
[ 1.600077] net eth0: phy found : id is : 0x7c0f1
[ 1.604893] libphy: PHY 4a101000.mdio:01 not found
[ 1.609709] net eth0: phy “4a101000.mdio:01” not found on slave 1, err -19
[ 1.622369] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 11.622036] Waiting up to 110 more seconds for network.
[ 21.622035] Waiting up to 100 more seconds for network.
[ 31.622025] Waiting up to 90 more seconds for network.
[ 41.622038] Waiting up to 80 more seconds for network.
[ 51.622028] Waiting up to 70 more seconds for network.
[ 61.622023] Waiting up to 60 more seconds for network.
[ 71.622032] Waiting up to 50 more seconds for network.
[ 81.622023] Waiting up to 40 more seconds for network.
[ 91.622025] Waiting up to 30 more seconds for network.
[ 96.002045] random: nonblocking pool is initialized
[ 101.622030] Waiting up to 20 more seconds for network.
[ 111.622026] Waiting up to 10 more seconds for network.
[ 121.622030] Waiting up to 0 more seconds for network.
[ 121.642057] Sending DHCP requests … timed out!
[ 210.072933] IP-Config: Retrying forever (NFS root)…
[ 210.078089] net eth0: initializing cpsw version 1.12 (0)

Or is this a limitation of my hardware setup - only using IPoverUSB and no real eth connecting host and BBB. Could you kindly suggest me some debugging methods to fix this issue. Thank you!

Best regards,
Vishnu