注意

• DD-WRT重開機之後，通常需要1-2分鍾連上PPTP VPN, 實際連上去的速度視情況而定，所以別急著重開機就馬上上網。
• 重開機完成1-2分鍾後，您可以在電腦測試打開 http://whatismyip.org 這時您看到的IP應該是您VPN gateway的public IP, 而打開 http://myip.cn則是看到國內IP， 這兩個IP如果不一樣就成功了
• 如果兩個IP始終一樣，你可以查看autoddvpn.log, 方法如下：

如何查看log

您需要ssh進入DD-WRT， 並且查看/tmp/autoddvpn.log， pptp+wget為例子內容如下：

[INFO#445] 01/Jan/1970:00:00:26 log starts [INFO#445] 01/Jan/1970:00:00:26 getting vpnup.sh <--網路取得vpnup.sh [INFO#445] 01/Jan/1970:00:00:41 getting vpndown.sh <--網路取得vpndown.sh [INFO#445] 01/Jan/1970:00:00:41 modifying /tmp/pptpd_client/ip-up [INFO#445] 01/Jan/1970:00:00:42 /tmp/pptpd_client/ip-up not exists, sleep 10sec. [INFO#445] 01/Jan/1970:00:00:52 /tmp/pptpd_client/ip-up modified [INFO#445] 01/Jan/1970:00:00:52 modifying /tmp/pptpd_client/ip-down [INFO#445] 01/Jan/1970:00:00:52 /tmp/pptpd_client/ip-down modified [INFO#445] 01/Jan/1970:00:00:52 ALL DONE. Let's wait for VPN being connected.  <-- 前置准備動作完成，等待pptp撥號成功 [INFO#722] 06/Aug/2010:10:21:04 vpnup.sh started <-- 撥號成功了，開始進行vpnup.sh動作 [INFO#722] 06/Aug/2010:10:21:25 preparing the exceptional routes [INFO#722] 06/Aug/2010:10:21:25 modifying the exceptional routes [INFO#722] 06/Aug/2010:10:21:25 fetching exceptional routes for flickr [INFO#722] 06/Aug/2010:10:21:25 adding 68.142.214.43 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 adding 69.147.90.159 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 adding 69.147.90.215 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 adding 67.195.19.66 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 adding 67.195.19.74 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 adding 68.142.214.24 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 fetching exceptional routes for dropbox [INFO#722] 06/Aug/2010:10:21:26 adding 174.129.27.0/24 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 adding 184.73.211.0/24 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 adding 204.236.220.0/24 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 fetching exceptional routes for vimeo [INFO#722] 06/Aug/2010:10:21:26 adding 66.235.126.128 via wan_gateway [INFO#722] 06/Aug/2010:10:21:26 fetching exceptional routes for nexttv [INFO#722] 06/Aug/2010:10:21:26 adding 210.242.234.154 via wan_gateway [INFO#722] 06/Aug/2010:10:21:27 adding 96.17.8.110 via wan_gateway [INFO#722] 06/Aug/2010:10:21:27 adding 203.69.113.0/24 via wan_gateway [INFO#722] 06/Aug/2010:10:21:27 modifying custom exceptional routes if available [INFO] 06/Aug/2010:10:21:28 vpnup.sh ended  <--- vpnup.sh完成，到這裡應該基本OK了

或者也可以在DD-WRT的web管理界面的命令輸入框打 cat /tmp/autoddvpn.log 然後按下Run Command, 也會傳回LOG記錄。

log看起來正常但是還是無法翻牆？

進入DDWRT下這個指令

root@DD-WRT:~# route -n | tail -n 20 112.224.0.0     192.168.172.254 255.224.0.0     UG    0      0        0 vlan2 122.64.0.0      192.168.172.254 255.224.0.0     UG    0      0        0 vlan2 110.192.0.0     192.168.172.254 255.224.0.0     UG    0      0        0 vlan2 60.0.0.0        192.168.172.254 255.224.0.0     UG    0      0        0 vlan2 58.32.0.0       192.168.172.254 255.224.0.0     UG    0      0        0 vlan2 182.96.0.0      192.168.172.254 255.224.0.0     UG    0      0        0 vlan2 180.96.0.0      192.168.172.254 255.224.0.0     UG    0      0        0 vlan2 61.128.0.0      192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 111.0.0.0       192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 223.64.0.0      192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 59.192.0.0      192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 117.128.0.0     192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 183.192.0.0     192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 183.0.0.0       192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 113.64.0.0      192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 120.192.0.0     192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 116.128.0.0     192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 112.0.0.0       192.168.172.254 255.192.0.0     UG    0      0        0 vlan2 127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo 0.0.0.0         192.168.199.1   0.0.0.0         UG    0      0        0 ppp0

注意最後一行，這是你的default GW也就是VPN GW， 上面這個例子VPN GW是192.168.199.1 你可以直接ping這個IP， 正常情況下應該要有穩定持續不掉包的返回，如果沒有返回或是有掉包情況，這樣會導致你的VPN連線很不穩定，這通常可能是你的ISP到境外VPN主機網路不穩定造成的。

ping VPN GW返回很正常但是還是無法翻牆

1. 請確定 http://whatismyip.org 看到的的確是國外IP
2. 可以ping到VPN GW
3. 在Windows or Mac下使用traceroute or tracert指令對8.8.8.8查詢，例如

macbook-2:~ macbook$ traceroute -n 8.8.8.8 traceroute to 8.8.8.8 (8.8.8.8), 64 hops max, 52 byte packets
 1  10.0.1.1  5.454 ms  0.737 ms  3.562 ms
 2  192.168.199.1  401.621 ms  395.949 ms  405.031 ms
 3  74.82.169.65  412.484 ms  395.876 ms  402.661 ms
 4  172.18.0.65  394.927 ms  411.505 ms  391.229 ms
 5  172.18.201.1  388.315 ms  400.306 ms  395.004 ms ...

注意第二跳應該是你的VPN GW IP。

4. 如果1-3都沒問題了，但是某些網站例如Facebook Youtube Twitter還是打不開，表示你很可能被DNS污染了， 你需要先關閉所有瀏覽器，然後：

在Mac下用

$ dscacheutil -flushcache

來清除cache 或Windows下用

$ ipconfig /flushdns

來清除被污染的DNS cache即可。