I want to share my wifi airport (en0) via my ethernet connection (en5) on my MacBook Pro

This article looks promising, but the first posting applies to OLD 10.7.4.

Read the second and subsequent postings.

https://apple.stackexchange.com/questions/52479/changing-the-range-of-addresses-served-to-clients-connected-via-internet-sharing

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The hotspot created by your Mac acts as software-only Router on behalf of your connected downstream devices.

Your Mac does NOT connect your downstream devices DIRECTLY to the office network using the same (possibly conflicting) IP addresses. Its software-only Router does a Network Address Translation. All requests from downstream devices will appear to originate from your valid, office-issued, local IP address. All responses from the Internet will be Network-Address Translated back before being sent to the correct devices downstream. As always, unsolicited responses are discarded.

The actual address of devices downstream are of no importance, because they are never presented directly to your office Network.

<<Here a confliction comes.>>

There is no conflict because the addresses issued by your Mac are only seen by downstream devices. All requests going to the Internet will have their local addresses changes using Network Address Translation before being presented to your office Network for Routing.

Just be sure you are making the connection to the correct Wi-Fi Network, by SSID (which most people see as "Network-name")

<<What do you mean by Network-name ? Is it a WIFI SSID name >>

yes, exactly.

andysunqd wrote:

Hello experts,

I want to share my wifi airport (en0) via my ethernet connection (en5) on my MacBook Pro (10.14.4 version). So I can access the hotspot on my phone.

Best Regards,

Andy

I'm sorry but could you please rehrase the above statement. Are you saying you want to connect to two networks at the same time? If so, you can't.

Changing the default IP address used by Ethernet Sharing requires probing deep under the hood. There is no simple article that tells how to change it.

Apple chose that number because it would suit most situations, and not conflict with the obvious choices that would exist on most Networks. Your network administrator is either "way too smart", or should go to work for Apple.

If you want to provide a Wi-Fi hotspot form your Mac, there is no need to have a unique IP address, only a unique Network-name. I am sure you do not automatically get the same Network-name as your work Wi-Fi.

Then be certain to connect to the correct Network, and you are online.

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Imagine the case of two neighbors who both subscribe to the same service. Chances are they will get the same Router, and it will default to the same local IP address. But because the Network-names are unique, there is no confusion.

The first poster on that discussion is talking about 10.7.4.

The second poster is talking about 10.11 El Capitan. so that has much more chance of working.