用iptables改TTL就知道電信業者是不是利用TTL判斷是否使用分享

 Modifying the TTL

The Time To Live is the maximum number of routers a packet will travel through before it is discarded. In certain situations, it may prove useful to increase it (typically) in order to make your network more reliable.

Example 1: Set the incoming TTL to 10, before the router routes it into the LAN

iptables -t mangle -I PREROUTING -i `get_wanface` -j TTL --ttl-set 10

Example 2: Set the outgoing TTL to 128, just as if a Windows machine was connected directly to the modem.

iptables -t mangle -I POSTROUTING -o `get_wanface` -j TTL --ttl-set 128

Example 3: Try to hide the fact that an outgoing packet was routed, by incrementing the TTL by one.

iptables -t mangle -I POSTROUTING -o `get_wanface` -j TTL --ttl-inc 1