Configuration Precautions for Basic WLAN Services
VLAN Deployment
Packets transmitted on a WLAN include management packets and service data packets.
- Management packets must be forwarded through Control And Provisioning of Wireless Access Points (CAPWAP) tunnels.
- Service data packets can be forwarded directly or through CAPWAP tunnels.
In practice, management packets and service data packets must have different VLANs configured. That is, management packets must have management VLANs configured, and service data packets must have service VLANs configured.
- Management VLAN: transmits packets that are forwarded through CAPWAP tunnels, including management packets and service data packets forwarded through CAPWAP tunnels.
- Service VLAN: transmits service data packets.
You are not advised to use VLAN 1 as the management VLAN or service VLAN.
Management VLAN and service VLAN must be different.
- When an AP connects to an AC through a Layer 2 network, VLAN m is the same as VLAN m', and VLAN s is the same as VLAN s'.
- When an AP connects to an AC through a Layer 3 network, VLAN m is different from VLAN m', and VLAN s is different from VLAN s'.
Figure 4-29 shows the process of forwarding management packets through CAPWAP tunnels.
In Figure 4-29:
- In the uplink direction (from the AP to the AC): When receiving management packets, the AP encapsulates the packets in CAPWAP packets. The switch tags the packets with VLAN m. The AC decapsulates the CAPWAP packets and removes the tag VLAN m'.
- In the downlink direction (from the AC to the AP): When receiving downstream management packets, the AC encapsulates the packets in CAPWAP packets and tags them with VLAN m'. The switch removes the tag VLAN m from the packets. The AP decapsulates the CAPWAP packets.
Figure 4-30 shows the process of directly forwarding service data packets.
In Figure 4-30, service data packets are not encapsulated in CAPWAP packets.
- In the uplink direction (from the STA to the Internet): When upstream service data packets in 802.11 format are sent from the STA to the AP, the AP converts the packets into 802.3 packets, tags the packets with VLAN s, and forwards the packets to the destination.
- In the downlink direction (from the Internet to the STA): When downstream service data packets in 802.3 format reach the AP (the packets are tagged with VLAN s' by upstream devices), the AP converts the 802.3 packets into 802.11 packets and forwards them to the STA.
Figure 4-31 shows the process of forwarding service data packets through CAPWAP tunnels.
In Figure 4-31, service data packets are encapsulated in CAPWAP packets and transmitted through CAPWAP data tunnels.
- In the uplink direction (from the STA to the Internet): When upstream service data packets in 802.11 format are sent from the STA to the AP, the AP converts the packets into 802.3 packets, tags the packets with VLAN s, and encapsulates them in CAPWAP packets. The upstream switch tags the packets with VLAN m. The AC decapsulates the CAPWAP packets and removes the tag VLAN m' from the packets.
- In the downlink direction (from the Internet to the STA): When downstream service data packets reach the AC, the AC encapsulates the packets in CAPWAP packets, allows the packets carrying VLAN s to pass through, and tags the packets with VLAN m'. The switch removes VLAN m from the packets. The AP decapsulates the CAPWAP packets, removes VLAN s, converts the 802.3 packets into 802.11 packets, and forwards them to the STA.
Management VLAN tag VLAN m is the outer tag of CAPWAP-encapsulated packets. The intermediate devices between the AC and AP only need to transparently transmit VLAN m and do not need to be configured with VLAN s encapsulated in the CAPWAP packets.
In Figure 4-32, to implement direct forwarding, ensure that the AP can exchange management VLAN packets with the AC and exchange service VLAN packets with upstream devices.
In Figure 4-33, to implement tunnel forwarding, ensure that the AP can exchange management VLAN packets with the AC and the AC can exchange service VLAN packets with upstream devices.
