Layer 2 bridging of the perspective Router

The second layer of the router's bridging function is actually the ability to process data frames. When a vro enables a "sub-interface", multiple data frame encapsulation such as ISL and 802. 1Q are supported. In this way, we can use a router to connect to a layer 2 device that uses different frames to encapsulate the standard.

Cisco routers provide Integrated Routing and Bridging, IRB) functions. When IRB is configured, protocol data streams that are not routable can be switched over ports configured as the same bridge group, protocol data streams that can be routed are routed between other routing ports or different bridge groups.

You can add sub-interfaces to different bridge groups. Each bridge-group corresponds to a BVI Virtual Interface, routing Between Different BVI or between BVI and other ports can be achieved.

If the two switches want to use a unified VLAN division, that is, enable the clients connected to VLAN 1 of SW1 and the clients connected to VLAN 1 of SW2 to use the same network segment and the same gateway, and the clients connected to VLAN 2 of SW1 and the clients connected to VLAN 2 of SW2 use the same network segment and the same gateway. In this case, the Layer 2 bridging function of the router needs to be enabled.

The vro configuration is described as follows:

Enable two sub-interfaces F0/0.1 and F0/0.2 on the F0/0 interface of the router, both of which adopt ISL frame encapsulation:

Int f0/0.1

Encapsulation ISL 1

Int f0/0.2

Encapsulation ISL 2

Enable two sub-interfaces F0/1.1 and F0/1.2 On the F0/1 interface of the router, both of which adopt the 802.1Q frame encapsulation:

Int f0/1.1

Encapsulation dot1q 1

Int f0/1.2

Encapsulation dot1q 2

Add F0/0.1 and F0/1.1 to the bridge group bridge-group 1:

Int f0/0.1

Bridge-group 1

Int f0/1.1

Bridge-group 1

Add F0/0.2 and F0/1.2 to bridge group 2:

Int f0/0.2

Bridge-group 2

Int f0/1.2

Bridge-group 2

Create bridge-group 1 and 2 in global mode:

Bridge 1 protocol ieee // the ieee option here enables the IEEE Spanning Tree protocol

Bridge 2 protocol ieee

Specify the protocol to be bridging in global mode:

Bridge 1 route ip

Bridge 2 route ip

Enable integrated routing and bridging in global mode:

Bridge irb

Create a BVI logical port and configure the IP Address:

Interface bvi 1

Ip add 192.168.1.1 255.255.255.0

Interface bvi 2

Ip add 192.168.2.1 255.255.255.0

1. Application of the router bridging function in VLAN Division
2. Differences between bridging, switching, and Routing