VPN client cannot receive packets

[Zhi-Qiang Lei]

I setup a L2TP/IPsec VPN as this article:

http://wiki.stocksy.co.uk/wiki/L2TP_VPN_in_FreeBSD

My problem is that the connected clients cannot receive packets, however, sending is okay.

Here are the tcpdump results if I tried to ping 8.8.8.8:

root at 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

What could be wrong? And how can I troubleshoot? You may reply on SuperUser if you want, thanks in advance.

http://superuser.com/questions/816485/cannot-receive-packets

Best regards,
Zhi-Qiang Lei
zhiqiang.lei at gmail.com