Q:

FreeBSD L2TP VPN connection error

I have a L2TP/IPsec VPN server on FreeBSD 10 set as this article.  Everything works fine except clients cannot receive packets from outside. 
Here is the tcpdump result when a connected client tries to ping 8.8.8.8:
root@freebsd-7638:~ # tcpdump -i vtnet0 icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on vtnet0, link-type EN10MB (Ethernet), capture size 65535 bytes
05:55:17.630770 IP 192.168.99.150 > google-public-dns-a.google.com: ICMP echo request, id 36697, seq 0, length 64
05:55:18.627825 IP 192.168.99.150 > google-public-dns-a.google.com: ICMP echo request, id 36697, seq 1, length 64
05:55:19.624058 IP 192.168.99.150 > google-public-dns-a.google.com: ICMP echo request, id 36697, seq 2, length 64
05:55:20.618946 IP 192.168.99.150 > google-public-dns-a.google.com: ICMP echo request, id 36697, seq 3, length 64
05:55:21.622551 IP 192.168.99.150 > google-public-dns-a.google.com: ICMP echo request, id 36697, seq 4, length 64

On the other hand, the ping results are always timeout. 
What could be the problem?  Where shall I check?  Another thing I noticed is that sometimes there are packets from Google DNS to the VPN server but the client, could it be a NAT problem?  Thanks. 

A:

It turns out to be a known issue of 10.0-RELEASE.