notes: Bridging

Transparent bridging
- is using normal STP rules
- same election root bridge and root port election

Router in bridge mode doesnt support the sys-id-ext, brigde priority will always be 32768 for any vlan which will make the router as a root bridge.

enabling transparent bridging on routers:

step1: enable bridging:

bridge # protocol ieee

step2: bind to the interfaces:

interface fa0/1
bridge-group #

for frame-relay interfaces:

interface s0/0
encapsulation frame-relay
frame-relay map bridge dlci# broadcast
bridge-group #


CRB (concurrent Routing and Bridging)
- this protocol can be routed on one interface while being bridged on another interface.
- When CRB is used traffic in the routed domain cannot be passed onto the bridge domain.
- CRB is considered legacy since IRB includes all the functionality of CRB with the addition of the BVI.


IRB (Integrated Routing and Bridging)
- this protocol can be both routed and bridged on the same interface.
- When IRB is used traffic from the routed domain can be passed onto the bridge domain.


enabling IRB:

1. Create transparent bridge group

bridge # protocol ieee

2. Enable IRB and what to be bridged

bridge irb
bridge # route ip

bridge # bridge ip
-on by default

3. Enable routing & bridging for the bridge-group under the interface

interface fa0/0
bridge-group #

4. Configure BVI to connect the bridged and routed domain

interface BVI #
ip add 1.1.1.1 255.255.255.0

Fallback Bridging (VLAN bridging)
used to bridge non-routed or non-supported protocols (SNA, DECNet, AppleTalk, etc.)
to communicate across VLANs and routed ports. one good implementation also is bridging IPv6.

enabling VLAN bridging

1. Specify the bridging VLAN

bridge # protocol vlan-bridge

2. Assign the SVI and routed port to this bridge.

interface vlan1
bridge-group #

interface fa0/1
no switchport

bridge-group #

verification:

sh bridge # group