[c-nsp] Problem on LNS VRF

[Alfred Yip]

Dears,
I have an ASR1001 functioning as a LNS. User will use a 3G Modem to
establish PPPoE to Provider's LAC and then terminate at the LNS via L2TP
tunnel. I have assigned certain users to their proper VRF  through AAA
server so that it can be applied their peer ip, vrf and loopback interface
on the virtual-access interface. 3G Modem can establish the connection to
LNS and assign the VAI to specific VRF according to the return av-pair
attribute. LNS also has another sub-interface to the PE router and assigned
to the same VRF with the VAI for each user. However, I found that I can't
ping from the 3G Modem to PE, on the contrary, PE can ping to the 3G Modem.
The traceroute result from 3G Modem is stuck at the LNS and I can ping from
the 3G Modem to LNS. I have checked that the vrf routing table on LNS has
the route to PE. It's so strange that the 3G Modem can reach the LNS but
not PE. Any idea??