The source field is the Ethernet frame field containing the sender’s source MAC address. It identifies the port that transmitted the frame and supports hop-to-hop delivery at Layer 2. section 6.2.2
Key points:
- A MAC address is 6 bytes, or 48 bits, and is usually written as 12 hexadecimal characters. section 6.2.2
- A switch uses the source MAC address to learn which port leads to a host; it uses the destination MAC address to forward the frame. section 6.2.2
Switch learning
When a frame arrives, the switch records the source MAC address against the receiving port. Later, that information helps the switch forward frames toward that host. section 6.2.2
Table 6.1 Decimal numbers and their hexadecimal equivalents (view table figure)
| Dec. |
Hex. |
Dec. |
Hex. |
Dec. |
Hex. |
Dec. |
Hex. |
|||
|---|---|---|---|---|---|---|---|---|---|---|
| 0 |
0 |
8 |
8 |
16 |
10 |
24 |
18 |
|||
| 1 |
1 |
9 |
9 |
17 |
11 |
25 |
19 |
|||
| 2 |
2 |
10 |
A |
18 |
12 |
26 |
1A |
|||
| 3 |
3 |
11 |
B |
19 |
13 |
27 |
1B |
|||
| 4 |
4 |
12 |
C |
20 |
14 |
28 |
1C |
|||
| 5 |
5 |
13 |
D |
21 |
15 |
29 |
1D |
|||
| 6 |
6 |
14 |
E |
22 |
16 |
30 |
1E |
|||
| 7 |
7 |
15 |
F |
23 |
17 |
31 |
1F |
Use the decimal-to-hexadecimal table to read the notation used for 48-bit MAC addresses. section 6.2.2
