# Q1B · Expand an IPv6 address

Subject: Computer Networks

Exam: M2

Reader: https://deep-learning-study-room.vercel.app/cn/#m2/mocks/mock-b/q1b

Canonical: https://deep-learning-study-room.vercel.app/read/cn/m2/mocks/mock-b--q1b/

Q1(a)+Q1(b) compulsory; choose any two of Q2/Q3/Q4 · 10 marks attempted

### Question. Expand 2001:db8::10 into full IPv6 notation and state the number of groups replaced by ::. [2 practice marks]

#### Answer

## Given

Given address: `2001:db8::10`.

## To find

The full 128-bit address in eight-group hexadecimal notation.

## Formula and why



$$
\text{missing groups}=8-\text{visible groups}
$$



A written 0 is a visible group. :: represents only the omitted all-zero groups.

## Step-by-step solution

#### Step 1. Count groups on both sides

Left: 2001, db8 (2 group(s)). Right: 10 (1 group(s)).

#### Step 2. Calculate omitted groups

Visible=2+1=3. Missing=8−3=5.

#### Step 3. Insert the groups

`2001:db8:0:0:0:0:0:10`.

#### Step 4. Pad each group on the left

| Group number | Four-digit group |
| --- | --- |
| 1 | 2001 |
| 2 | 0db8 |
| 3 | 0000 |
| 4 | 0000 |
| 5 | 0000 |
| 6 | 0000 |
| 7 | 0000 |
| 8 | 0010 |

#### Step 5. Write all eight in order

`2001:0db8:0000:0000:0000:0000:0000:0010`.

**Final answer:** `2001:0db8:0000:0000:0000:0000:0000:0010`

#### What this result means

Leading zeros change the spelling, not the address value. The final group count is eight.