Why did it work with the second address specified, but not the first?

You created an IP address for interface not.3 with the following command, which executed
successfully:
ipadm create-addr T static a 192.168.0.100/24 net3/v4

You then ran:
ipadm showif
The result indicated that the interface was down.
You then ran:
ipadm delete-addr net3/v4
ipadm create-addr T static a 192.168.0.101/24 net3/v4
ipadm show-if
The last command indicated that the interface was up.
Why did it work with the second address specified, but not the first?

A.
The 192.168.0.100 address is reserved for broadcast messages.

B.
Another device exists on the network, using the 192.168.0.100 address.

C.
The network interface card does not support the address 192.168.0.100.

D.
The address 192.168.0.100 is at a boundary and may not be configured in Oracle Solaris 11.

E.
192.168.0.100 is a DHCP address and may not be statically configured in Oracle Solaris 11.

Explanation:
The first IP address is already in use.