📘 CCNA 200-301 v1.1
1.11 Describe wireless principles
1.11.b SSID
🔹 What is an SSID?
SSID stands for Service Set Identifier.
It is the name of a wireless network (Wi-Fi network) that devices use to identify and connect to the correct Wireless LAN (WLAN).
In simple terms:
The SSID is like the “network name” that wireless clients (like laptops, phones, or access points) use to recognize and join a specific wireless network.
🔹 Purpose of the SSID
- The main purpose of an SSID is to uniquely identify a wireless network.
- In an environment where there may be many wireless networks (for example, in an office building with multiple departments), the SSID helps users and devices find and connect to the correct one.
🔹 How SSID Works
- Broadcasting:
- The Access Point (AP) or wireless router sends out beacon frames that contain the SSID and other network information.
- This broadcast lets wireless clients see available networks when they scan for Wi-Fi.
- Association:
- When a client selects an SSID to connect to, it sends a probe request to the access point with that SSID.
- The access point responds if it supports that SSID, and then the client starts the authentication and association process.
- Communication:
- Once connected, all wireless traffic between that client and the AP includes the SSID to make sure it’s part of the correct network.
🔹 SSID Configuration
An SSID is configured on a Wireless Access Point (AP) or Wireless LAN Controller (WLC).
- You can assign one or multiple SSIDs to a single AP.
- Each SSID can be linked to a different VLAN or network segment.
📘 Example (IT context):
- An organization’s access point might have:
- SSID: Corp-WiFi → VLAN 10 (employees)
- SSID: Guest-WiFi → VLAN 20 (visitors)
This allows separating employee and guest traffic securely.
🔹 Hidden SSID
An SSID can be:
- Broadcast (visible):
The AP advertises the SSID in beacon frames. Clients can see and connect easily. - Hidden (non-broadcast):
The SSID is not included in beacon frames. Clients must manually enter the SSID to connect.
⚠️ Important for CCNA:
Hiding the SSID does not provide real security, because it can still be discovered using wireless sniffing tools.
It only hides the network name from basic users.
🔹 SSID Length and Case Sensitivity
- The SSID can be up to 32 characters long.
- It is case-sensitive.
(For example: “CCNA_WIFI” and “ccna_wifi” are different SSIDs.) - It can include letters, numbers, and some special characters.
🔹 SSID and BSSID (Do not confuse them!)
| Term | Meaning | Description |
|---|---|---|
| SSID | Service Set Identifier | The name of the wireless network (logical identifier). |
| BSSID | Basic Service Set Identifier | The MAC address of the Access Point’s radio interface (physical identifier). |
📘 So:
- All access points broadcasting the same SSID belong to the same Extended Service Set (ESS).
- But each access point still has a unique BSSID.
Example:
- SSID: Corp-WiFi
- AP1 BSSID: 00:11:22:33:44:55
- AP2 BSSID: 00:11:22:33:44:66
Both belong to the same WLAN but represent different physical APs.
🔹 Multiple SSIDs on a Single Access Point
Modern access points can broadcast multiple SSIDs at once — each associated with different VLANs and security settings.
Example in an IT environment:
| SSID | VLAN | Security Type |
|---|---|---|
| Corp-WiFi | 10 | WPA3-Enterprise |
| Guest-WiFi | 20 | WPA2-PSK |
| IoT-WiFi | 30 | WPA2-PSK |
This allows network segmentation and security control while using a single AP.
🔹 Security Considerations with SSID
- The SSID itself does not provide security — it is just an identifier.
- Real wireless security is achieved using authentication and encryption, such as:
- WPA2 or WPA3
- 802.1X (RADIUS) for enterprise networks
- However, using a meaningful SSID can help organize and manage multiple wireless networks effectively.
🔹 SSID in Enterprise vs Home Environments
| Feature | Enterprise Network | Home/Small Office |
|---|---|---|
| Number of SSIDs | Usually multiple (e.g., Corp, Guest, IoT) | Usually one |
| Authentication | WPA2/WPA3-Enterprise (802.1X) | WPA2/WPA3-Personal (Pre-shared key) |
| VLAN Mapping | Yes (each SSID → different VLAN) | Usually no VLANs |
| Controller Use | Centralized management using WLC | Managed through router UI |
🔹 Key Points to Remember for CCNA Exam
✅ SSID = Name of the WLAN (logical identifier).
✅ Can be up to 32 characters and is case-sensitive.
✅ Access Points broadcast SSIDs through beacon frames.
✅ Clients connect by choosing the correct SSID.
✅ Multiple SSIDs can exist on one AP (mapped to VLANs).
✅ Hidden SSIDs are not secure — just not broadcast.
✅ Each SSID belongs to a Basic Service Set (BSS) or Extended Service Set (ESS).
✅ SSID ≠ BSSID (SSID = logical name, BSSID = MAC of AP radio).
🧠 Summary
- SSID uniquely identifies a Wireless LAN.
- Access Points broadcast it to let clients connect.
- Clients must select the correct SSID to join the right network.
- Multiple SSIDs allow network segmentation.
- Hiding SSID doesn’t secure the network — encryption does.
