Indestructible wall in Minecraft?

I have seen on servers that there's often a blue and white striped indestructible abes wall, so to speak

Since I wanted to ask if there may be a command for it

If so please write in the comments

https://minecraft-de.gamepedia.com/...ltbarriere

That's the wall you mean…

This is the Worldboarder.

The Worldboarder is implemented in Vanilla, and is in every world except that this wall is really big. To be exact 999999999 blocks! (yes 7 times the 9)

You can change the size of this border belibig. Go to your world, center yourself around the boarders, and enter:

/ https://minecraft.gamepedia.com/...orldborder center ~ ~
With that you've centered the Worldboarder. Now you have to define the size:

/ worldborder set 10

In this case, 10 is the block radius around which the border is set.

Remarks:

All commands with the Worldboarder https://minecraft.gamepedia.com/...rld_border

You can execute commands through commandblocks, creating a wall like servers
You can also let the boarder slide so that it slowly expands or shrinks.
I would not be happy about a "most helpful answer".