Answer
2001:0db8:cafe:4500
Explanation:
There are total 8 hexadecimal numbers that are separated by a semi colon in IPv6 IP address. It contains two type of information.
1. Network Identifier (The information about network)
2. Host Identifier (The information About Host)
Upper four hexadecimal numbers are called Network Identifier and Lower 4 are called Host Identifier.
For Example
2001 : 0db8 : cafe : 4500 : 1000 : 00d8 : 0058 : 00ab
This is the IPv6 IP address given in Question.
Upper four number are given as:
2001 : 0db8 : cafe : 4500
This is called Network Identifier.
The lower Four numbers are 1000 : 00d8 : 0058 : 00ab called Host identifier.