These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.53 s (backtrack: 0/20).

[ebuild  N     ] net-libs/libnet-1.3-r1:1.1::gentoo  USE="-man -static-libs -test" 603 KiB
[ebuild  N     ] net-analyzer/arping-2.25:2::gentoo  USE="filecaps seccomp -test" 61 KiB
[blocks B      ] net-misc/iputils[arping(+)] ("net-misc/iputils[arping(+)]" is soft blocking net-analyzer/arping-2.25)

Total: 2 packages (2 new), Size of downloads: 663 KiB
Conflict: 1 block (1 unsatisfied)

 * Error: The above package list contains packages which cannot be
 * installed at the same time on the same system.

  (net-misc/iputils-20250605-r3:0/0::gentoo, installed) pulled in by
    net-misc/iputils required by @system 

  (net-analyzer/arping-2.25:2/2::gentoo, ebuild scheduled for merge) pulled in by
    =net-analyzer/arping-2.25


For more information about Blocked Packages, please refer to the following
section of the Gentoo Linux x86 Handbook (architecture is irrelevant):

https://wiki.gentoo.org/wiki/Handbook:X86/Working/Portage#Blocked_packages