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Configuring bridging
MSR routers support only transparent bridging, so this document provides information about
transparent bridging only.
MSR routers do not support inter-VLAN transparent bridging but support VLAN transparent
transmission across Ethernet.
For interface modules MIM-16FSW, DMIM-24FSW, FIC-16FSW, and DFIC-24FSW, you cannot
configure the function of dropping unknown multicast packets in a VLAN whose VLAN interface has
joined a bridge set.
Overview
A bridge is a store-and-forward device connecting and transferring traffic between LAN segments at
the data-link layer. In some small-sized networks, especially those with a dispersed distribution of
users, bridges can reduce the network maintenance costs without requiring the end users to perform
special configurations on the devices.
Major bridging technologies include transparent bridging, source-route bridging (SRB), translational
bridging, and source-route translational bridging (SR/TLB). HPE devices support only transparent
bridging.
Transparent bridging bridges LAN segments of the same physical media type, primarily in Ethernet
environments. A transparent bridging device keeps a bridge table, which contains mappings
between destination MAC addresses and outbound interfaces.
Transparent bridging on a device provides the following features:
• Bridging over Ethernet
• Bridging over PPP and HDLC links
• Bridging over X.25 links
• Bridging over FR links
• VLAN transparency
• Support for both routing and bridging
Bridge functionality
Obtaining the bridge table
A bridge relies on its bridge table to forward data. A bridge table consists of two parts: MAC address
list and interface list. Once connected to a physical LAN segment, a bridge listens to all Ethernet
frames on the segments. When it receives an Ethernet frame, it extracts the source MAC address of
the frame and creates a mapping entry between this MAC address and the interface on which the
Ethernet frame was received.
As shown in Figure 101,
Hosts A, B, C, and D are attached to two LAN segments. Host A and Host B
are connected to bridge interface 1. When Host A sends an Ethernet frame to Host B, both bridge
interface 1 and Host B receive this frame.
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