DNS resolution failed for loopback IP URL

[HirenWU]

Dear Verizon team,

Our agent is using Verizon as preferred ISP.

We have configured loopback IP address (127.0.0.1) on our corporate DNS for agentpc.westernunion.com URL.

Whenever our Agent’s PC browser makes a call to this URL we are expecting to resolve it to loopback IP and through it invoke local services running on this PC from our application.

Lately many agents complaining that they are unable to resolve this URL causing disruption in services.

Both Agent & Company network team found nothing wrong with the setup.

Appreciate if you can check if anything is blocking DNS resolution for this URL at ISP side causing this issue.

[dslr595148]

While I do not work for Verizon, that IP Address is reservered only for loopback/testing.

Points to https://en.wikipedia.org/wiki/Reserved_IP_addresses

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Address block: 127.0.0.0/8

Address range: 127.0.0.0-127.255.255.255

Number of addresses: 16777216 

Scope: Host 

Description: Used for loopback addresses to the local host.

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RFCs(Request For Comments) # 1122, 6890, and 8190.

Also points to https://en.wikipedia.org/wiki/Localhost

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The local loopback mechanism may be used to run a network service on a host without requiring a physical network interface, or without making the service accessible from the networks the computer may be connected to. For example, a locally installed website may be accessed from a Web browser by the URL http://localhost to display its home page.

The name localhost normally resolves to the IPv4 loopback address 127.0.0.1, and to the IPv6 loopback address ::1.^[1]

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Opps. It would help for the public DNS entry that you use a public IP Address.

For westernunion.com you/they used a public IP Address but agentpc.westernunion.com you/they did not.

[EDIT] If you want to allow users to connect to 127.x.x.x, then they must have the server app on their computer and that server must be in the listening state.

[Cang_Household]

If you want to map agentpc.westernunion.com to an internal server IP, you would need to create a static DNS entry in your top level internal DNS server to point to the valid IP address of the server, not the loopback address.

Verizon DNS only relays name resolution for public websites.

[gs0b]

Welcome to the forums.  Know that you're talking mostly to other customers here.  If you want to talk to Verizon, you need to use their support channels.  The "contact us" link at the bottom of these pages will show you your options.

The previous posters have given you excellent advice.  If you have any questions, post a follow up and they will very likely respond.  Just remember we're users just like you, and all we know is what you tell us.

Another handy bit of info is that you can use "localhost" as a short-cut for "127.0.0.1".  If you truly want to have devices connect to themselves, you can use "localhost" in the URL and avoid any need to involve DNS.