# What is the source IP address when we ping 127.0.0.1?

**URL:** <https://forum.networklessons.com/t/what-is-the-source-ip-address-when-we-ping-127-0-0-1/3643>\
**Category:** CCNA R&S\
**Created:** [April 22, 2018, 2:55am UTC](https://forum.networklessons.com/t/what-is-the-source-ip-address-when-we-ping-127-0-0-1/3643 "2018-04-22T02:55:27Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![iqrar.patel92](https://cdn-forum.networklessons.com/letter_avatar_proxy/v4/letter/i/3be4f8/32.png) [@iqrar.patel92](https://forum.networklessons.com/u/iqrar.patel92)\
**Post date:** [April 22, 2018, 2:55am UTC](https://forum.networklessons.com/t/what-is-the-source-ip-address-when-we-ping-127-0-0-1/3643/1 "2018-04-22T02:55:27Z")

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Hi Rene,  
I was wondering, what would be the source IP address when we execute ping 127.0.0.1 ?

Thanks

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**Author:** ![ReneMolenaar](https://cdn-forum.networklessons.com/user_avatar/forum.networklessons.com/renemolenaar/32/488_2.png) [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)\
**Post date:** [April 24, 2018, 10:02am UTC](https://forum.networklessons.com/t/what-is-the-source-ip-address-when-we-ping-127-0-0-1/3643/2 "2018-04-24T10:02:50Z")

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Hi Iqrar,

That’s also 127.0.0.1. On a Linux device, you can see it if you capture the lo interface:

`sudo tcpdump -i lo -w local_traffic.pcap`

You can see a capture here:

> **[CS Personal on cloudshark.org](https://www.cloudshark.org/captures/89c0929a015b)**

Rene

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**Author:** ![iqrar.patel92](https://cdn-forum.networklessons.com/letter_avatar_proxy/v4/letter/i/3be4f8/32.png) [@iqrar.patel92](https://forum.networklessons.com/u/iqrar.patel92)\
**Post date:** [April 25, 2018, 5:56am UTC](https://forum.networklessons.com/t/what-is-the-source-ip-address-when-we-ping-127-0-0-1/3643/3 "2018-04-25T05:56:37Z")

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Thank you so much, Rene.

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**Author:** ![ReneMolenaar](https://cdn-forum.networklessons.com/user_avatar/forum.networklessons.com/renemolenaar/32/488_2.png) [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)\
**Post date:** [October 15, 2018, 2:44pm UTC](https://forum.networklessons.com/t/what-is-the-source-ip-address-when-we-ping-127-0-0-1/3643/4 "2018-10-15T14:44:58Z")

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A post was merged into an existing topic: [ARP (Address Resolution Protocol) explained](https://forum.networklessons.com/t/arp-address-resolution-protocol-explained/864/89)