Link Local Bridging

Link local bridging

Link local bridging is a wireless networking mechanism that

  • allows roaming wireless clients to use local services at their current point of attachment (PoA)

  • preserves access VLAN continuity during intra-controller and inter-controller roaming, and

  • reduces the need to tunnel client packets to their original anchor controller.

Feature history

Table 1. Feature history for link local bridging

Feature

 Release

Feature Information

Link Local Bridging

Cisco IOS XE 17.6.1

The Link Local Bridging feature allows you to manage link-local traffic in intercontroller and intracontroller roaming scenarios.

In Cisco IOS XE Bengaluru 17.5.x and earlier releases, only mDNS multicast link-local frames are forwarded.

Intra-controller and inter-controller roaming scenario

In Cisco IOS XE 17.5.1 and earlier releases, client packets were forwarded through the access VLAN of a client. The client also received all the IPv4 packets or all the IPv6 packets from its assigned access VLAN.

When an L3 client roamed from one controller to another controller, the point-of-presence (PoP) remained with the first controller, also known as the anchor controller or the home controller, and the point-of-attachment (PoA) moved to the second controller, also known as the foreign controller or the visited controller. In this anchor-foreign scenario, the client packets were tunneled back to the anchor controller to be forwarded on the access VLAN of the client.

Similarly, in case of L3 intra-controller roaming, when the feature Roaming Across Policy Profile is enabled, the client access VLAN is maintained, regardless of the policy profile VLAN. In such a scenario, the PoA becomes the destination policy profile VLAN.

A roaming wireless client benefits more from local services available near its PoA than from discovering services at its PoP.

Therefore, from Cisco IOS XE 17.6.1 onward, you can manage these intra-controller and inter-controller roaming scenarios with the Link Local Bridging feature. Link Local Bridging is disabled by default.

Use case

Enhancing Local Service Discovery for Roaming Clients with Link Local Bridging: If you use a local mode deployment and L3 roaming to manage clients moving across different physical locations, the Link Local Bridging feature allows wireless clients to discover nearby services, such as those advertised through mDNS, that are physically close to them. This ensures that, even as clients roam across subnets, they can still find and access local network services in their immediate vicinity.