Connectivity
Connectivity and managing Your Comcast Business network
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Hairpin/Loopback/NAT Reflection

Hello friends.

 

I have an access control program that wants to connect through a web-delivered program. I've set up port-forwarding, and it works fine when I'm outside the building. However, I can't reach it from inside the building. I assume because the source IP and destination IP are the same. 

 

Can anything be done for this? We're using whatever the standard Comcast Business router is. 

 

Thank you!

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Official Employee

Re: Hairpin/Loopback/NAT Reflection

Hi GlynnElectric and welcome to the business forums.

 

I wouldn't recommend having the source and destination IP the same. Also, I am not able to comment on these programs since they are not a product of Comcast Business and would be passed our demarcation. 

 

However, I can review your gateway and see if there are any issues with that. If you would like to do so, please private message me your first and last name, the name of your business, the full address and the phone number associated with your business account.

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Official Employee

Re: Hairpin/Loopback/NAT Reflection

Hi GlynnElectric and welcome to the business forums.

 

I wouldn't recommend having the source and destination IP the same. Also, I am not able to comment on these programs since they are not a product of Comcast Business and would be passed our demarcation. 

 

However, I can review your gateway and see if there are any issues with that. If you would like to do so, please private message me your first and last name, the name of your business, the full address and the phone number associated with your business account.

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Re: Hairpin/Loopback/NAT Reflection

This is the most absurd answer I ever heard! the problem with these comcast modem/router is trash! lack of features... 

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Official Employee

Re: Hairpin/Loopback/NAT Reflection

I am sorry to learn that our modems are not to your satisfaction. I will make sure to pass along your feedback. If you would like me to review your gateway to see if there are any issues, I would be happy to do so. Do you have any additional questions or concerns for me at this time? -Gabriel

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Trusted Forum Contributor

Re: Hairpin/Loopback/NAT Reflection

Assuming IPv4 Addressing:

 

How does the access control program determine the target IP address? There are various techniques that can be employed to utilize local addresses rather than global. A local-only DNS service can provide local IP addresses while global DNS service will use the site global IP address (gateway WAN IP address). Other techniques can include modifying the connection process to check for local access first, then fail over to global access. Use of these or similar techniques can supply provider and location independent access.

 

Editorial note:

 

This is the type of problem which does not have to exist using IPv6 addressing. For example, in the ususal Comcast default for IPv6, the address of a local system is globally reachable unless prevented by firewalling.

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