I'm running an Asus router with DDWRT connected to a Comcast cable modem (a Motorola SB5101U). The router is set up to update a dynamic dns entry. It's doing this, and the IP is correct (i.e.
nslookup gives the IP that my router thinks it has).
This IP is a 50.148.xxx.xxx IP, which is, to my knowledge, a public IP.
However, any attempt to ping this IP, or to send packets to any port on this router from external hosts (i.e. my shared web hosting box or school ssh server) end up in a blackhole.
While I'm on my home network, pinging my router's external IP does work.
Does anyone know what's going on?