Connectivity
Connectivity and managing Your Comcast Business network
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How to determine WAN IP Address from outside the LAN?

Hello,

 

When I am not at work I would like to be able to determine the WAN IP Address of the cable modem from the outside.

 

Is there an easy way to do that?

 

Thanks,

 

Bob

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Re: How to determine WAN IP Address from outside the LAN?

I would like to be able to get this information from the Comcast Business website.

 

However, I set up ddclient internally to update our DNS provider.  So I can get the info from them...

 

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Re: How to determine WAN IP Address from outside the LAN?

Bobcast,

 

Access whatsmyip or www.whatsmyip.org from any browser. You can see both IPv4 and IPv6 addresses.

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Re: How to determine WAN IP Address from outside the LAN?

That won't get WAN IP from outside the LAN. I would like to be proven wrong...

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Re: How to determine WAN IP Address from outside the LAN?

Orignal question;  When I am not at work I would like to be able to determine the WAN IP Address of the cable modem from the outside.

 

Clarification:

 

You can't get the WAN address of the cable modem, but can get the WAN IP address of the CPE router, which may or may not be inside the same physical box as the cable modem. 

 

For a local query, whatsmyip and the like will see the source IP address and report it.

 

For a remote query, the only certain way is to make use of a dynamic DNS service, where a local client request update of a DNS entry at suitable times. Then one can query DNS for the address from almost anywhere in the world. Of course, if you have static IP addressing from Comcast, the web site should have the addresses.

 

Side notes:

 

Many cable modems have a local IP address on the LAN. For example, 192.168.100.1 for an SB6121. This is for local management queries only. The modem is accessed from the Comcast by MAC address. and the local IP address is not visible on the Internet.

 

The local CPE router is a separate functional block, with the WAN IP addresses set by Comcast using static provisioning or dynamically using DHCP and the local LAN addressing is configured by Comcast using static provisioning or by local configuration for dynamic WAN addressing.

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