2.3 Given a scenario, select and configure wireless devices and technologies
Service Set Identifiers
📘CompTIA Network+ (N10-009)
BSSID (Basic Service Set Identifier)
Definition
- A BSSID is a unique identifier for a wireless access point (AP) or basic service set (BSS) in a Wi-Fi network.
- It helps devices distinguish between multiple Wi-Fi networks in the same area, even if they share the same network name (SSID).
Think of the BSSID as a digital fingerprint for an access point.
How It Works
- Every Wi-Fi access point (AP) has a BSSID.
- The BSSID is usually the MAC address of the AP’s wireless interface.
- Example:
00:1A:2B:3C:4D:5E
- Example:
- When your device scans for Wi-Fi networks:
- It sees the SSID (network name) — what humans recognize.
- It sees the BSSID — the actual access point providing the connection.
- If there are multiple access points with the same SSID, your device uses the BSSID to choose which AP to connect to.
Types of Wireless Networks Related to BSSID
- BSS (Basic Service Set)
- Standard Wi-Fi network with one AP.
- Has one BSSID, which is the AP’s MAC address.
- Example in IT: A single office AP serving a floor.
- IBSS (Independent Basic Service Set / Ad-Hoc)
- Wi-Fi network without an AP.
- Devices connect directly to each other.
- BSSID is randomly generated, not tied to a single AP.
- Example: Two laptops connecting directly for file sharing.
- ESS (Extended Service Set)
- Multiple APs sharing the same SSID to provide broader coverage.
- Each AP has its own BSSID.
- Devices use the BSSID to roam between APs without dropping the connection.
- Example: A company with several APs on the same Wi-Fi network across multiple floors.
Why BSSID Matters in IT
- Network troubleshooting:
- If a user has weak Wi-Fi, checking the BSSID helps identify which AP they are connected to.
- Load balancing and roaming:
- Devices switch to the AP with the strongest signal using the BSSID.
- Security monitoring:
- Network admins can track unauthorized APs by their BSSID.
Key Points for the Exam
- BSSID = MAC address of the AP (unique identifier).
- SSID = network name (human-readable).
- Multiple APs can share the same SSID, but each has a unique BSSID.
- BSSID helps devices and admins identify, connect, and manage Wi-Fi networks.
- BSS = 1 AP, ESS = multiple APs with roaming, IBSS = ad-hoc, no AP.
Simple Table for Quick Reference
| Term | Meaning | Example |
|---|---|---|
| SSID | Wi-Fi name visible to users | CompanyWiFi |
| BSSID | AP’s unique identifier (MAC address) | 00:1A:2B:3C:4D:5E |
| BSS | Single AP network | 1 AP on 2nd floor |
| ESS | Multiple APs, same SSID | Whole office coverage |
| IBSS | Ad-hoc network | Laptop-to-laptop sharing |
✅ Tip for remembering:
SSID is like a nickname for the network. BSSID is the AP’s ID card.
