ifconfig says my ip is 192.168.15.2. I believe this address is what ez-ipupdate is sending out to my DNS server. All I am using is a DSL modem. Isn't there supposed to be an outside IP address that gets sent to my DNS server? I always thought a 192 public IP was setup internally and assigned by my modem and the modem itself had its own address, which would be what is sent to the DNS server. I'm confused because I am having trouble pinging this address.

You can get your (current) IP address by visiting a site like whatismyip.org. If you don't have static ip (which usually might cost more than non-static one, though non-static ones try to stick with one ip if it's not reserved for somebody else), that could change when you reconnect.

192.xxx address space is reserved for internal networks. Public IP addresses start with something else, like 82.xxx for example; your DSL modem has a public IP and if you can connect more than one PC to your modem (i.e. it has more than 1 ethernet port in addition to the WAN port), then your DSL modem is also a router, which has it's own small dhcp server inside; every PC that connects to it, like your pc, gets it's own (ethernet) IP address, which is then masquared so that if several machines are connected to your DSL modem, they can all use the internet (which still goes trough only one public IP address) and to the outside world it seems like there was only one machine (one IP = your DSL modem); your DSL modem "hides" the machines behind it to an ethernet, and because your ISP only (usually) gives you one public IP, it is needed to be able to share the internet connection between all the machines simultaneously. Even if you had only one machine connected to the DSL modem, it still uses the public IP as it's own IP, and gives your machine an ethernet address one. The router may be able to do NAT'ing/masquerading for several programs/protocols, or then it may not. For example IRC and Messenger clients usually have a port range (especially Messenger) they use, and with Messenger it might produce problems; for example when you want to send a file, a send request is sent trough one port; an "answer" to that request might come back to another port (or then that goes to the correct port, file send is started but the other end communicates with the wrong port), and if your router/DLS-modem doesn't know where it should redirect the ports (to which of the machines), the connection doesn't work. So basically:

INTERNET <--> public ip address <--> DLS router <--> several machines with private ip addresses

If some things don't work, you might need to -- if it's possible with your modem/router -- set up port forwarding manually, i.e. tell the modem to which (local private) ip address it should send requests to some ports that it receives to it's public ip.

Awesome, now I get it. Thanks for explaining that.

As of right now all I have is a one port modem from SBC. So the 192.68.15.2 address is my private address. How do I find out what my public address is? Why is ez-ipupdate sending the private address to easydns? All the documentation I have read about this software makes it look so easy to configure, yet I am having a hard time. I have spent about a week each night trying to get it so I can at least ping my server from work.

I guess I need to next find out what NAT is.

NAT is what you dont understand right now. When you find your ip then you know what NAT is too. It change your "external" ip to your internal ip; your private network: 192.68.x.x


I dont know the software, and have never used the services either. But you will figure this out after the 2 other q's you have.

Looks like your on the right track here. Good luck!

at what point do you think that the internal address is being sent? dynamic client scripts often use whatismyipcom etc... themselves, or rather the dyndns provider had their own private equivalent. alternatively the source of the change request (i.e. after the address is natted) is used.

it is pulling it from the cache file.
/var/cache/ez-ipupdate/default-cache

I even went in and typed my public IP in the cache and reloaded. But it just over wrote the data with the private. So then I checked on easydns server and the hosts, which i had just deleted, entered it back in with the bad ip.

Here is what I pulled from my syslog:

Feb 22 21:31:48 mypc ez-ipupdate[13978]: version 3.0.11b8, interface eth0, host mypc.mydomain.com, server members.easydns.com, service easydns
Feb 22 21:31:48 mypc ez-ipupdate[13978]: got last update 192.168.15.2 on 2007/02/22 20:31 from cache file