Skip Links

Network World

Brad Reese

How to configure Transparent Bridging

By Brad Reese on Sun, 06/22/08 - 2:12pm.
Newsletter Signup

Cisco How-To Tutorials

Bridging is necessary when non-routable protocols like Network Basic Input/Output System (NetBIOS) and Local-Area Transport (LAT) are used to communicate between devices connected across different segments.

Bridging can also be configured for routable protocols instead of being routed.

Transparent Bridging (TB) is used to bridge networks using similar media.

TB is mostly used in an Ethernet environment.

A device configured for TB initially learns the location of the devices by looking at the source MAC addresses in the frames.

Next it builds a bridging table containing the MAC addresses and the ports through which they are reachable.

To forward or filter traffic on the ports, the destination address in the frames is compared with information in this table.

When there are multiple paths available between any two segments for providing redundancy, the spanning tree algorithm is used.

This prevents loops.

TB can either be remote or local.

Local bridges provide direct connections between LAN segments in the same site.

Remote bridges connect LAN segments at different sites, usually over WAN links.

To resolve this issue, perform these steps:

1. To configure bridging for a protocol, disable routing for that protocol.

Cisco routers route IP by default and bridge all other protocols.

To bridge IP, disable IP routing by issuing the no ip routing command from global configuration mode.


2. To configure bridging, create a bridge group by issuing the bridge bridge-group protocol {dec | ieee} command from global configuration mode.

3. To identify redundant paths and prevent bridging loops, choose either DEC or IEEE as the Spanning Tree Protocol (STP).

4. The router can act as multiple bridges and frames are bridged only among interfaces belonging to the same bridge group.

This grouping feature is commonly used to separate networks or users.

To include interfaces under the defined bridge group, issue the bridge-group bridge-group command under the interfaces.

This command can be used on WAN interfaces using any PPP (like High-Level Data Link Control [HDLC]) for remote bridging across the link.


5. Remote TB can also be configured over an X.25 or Frame Relay network.

Issue the x25 map bridge or frame-relay map bridge command under the specific physical interface or multipoint subinterface.


For sample configurations refer to:

Configuring Transparent Bridging

The above document includes the following configuration scenarios:

Example 1: Simple Transparent Bridging

Example 2: Transparent Bridging with Multiple Bridge Groups

Example 3: Bridging Over a Wide Area Network

Example 4: Remote Transparent Bridging Over X.25

Example 5: Remote Transparent Bridging Over Frame Relay With No Multicast

Example 6: Remote Transparent Bridging Over Frame Relay With Multicast

Example 7: Remote Transparent Bridging Over Frame Relay With Multi Sub-Interfaces

Example 8: Remote Transparent Bridging Over Switched Multimegabit Data Service (SMDS

Example 9: Remote Transparent Bridging With Circuit Group


View more Cisco How-To Tutorials

Contact Brad Reese
http://www.BradReese.Com

Brad's Top 5 Story Picks
# 1. Meet world's first CCIE at Cisco Live! Orlando: Terry Slattery will be in booth #249 - Chesapeake Netcraftsmen
# 2. Closer look: sFlow better than NetFlow?
# 3. Cisco CBQoS delivers powerful QoS policy metrics
# 4. Aruba scoffs at new Cisco mobility markitecture
# 5. Superior RF design: Meru outperforms Cisco by 76%, Aruba by 59%
Story Archives Brad Reese on Cisco Story Archives

Cisco Jobs

Cisco Repair

Cisco Resumes

Cisco Power Supplies

  

Welcome, visitor. Register Log in
About Brad Reese on Cisco

Brad Reese cofounded BradReese.Com Cisco Refurbished, which enables affordable networks globally by assuring customer satisfaction with guaranteed one year warranties on both Cisco Repair as well as Refurbished Cisco.

Don't be shy, contact Brad Reese online or call him Toll Free:

866-864-0506

International callers may wish to call Brad by dialing:

850-364-4115

Archives
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
Categories
A classic scam to defraud Cisco's SMARTnet program
America's Best profile written by Useem regarding Chambers' success
Avian Securities Senior Telecom Research Analyst - Catharine Trebnick
Breakingviews.com correspondent - Robert Cyran
CCIE
Careers
Charlie Giancarlo - Managing Director of Silver Lake Partners and Skype investor
Cisco
Cisco ASR 9000 architecture
Cisco ISR G2 Module Support
Cisco Integrated Services Router Generation 2 (ISR G2) Model Comparison
Cisco Integrated Services Routers Generation 2 Portfolio
Cisco Unified Communications Support for Microsoft Windows 7
Cisco is pushing their ASR 9000 at very competitive prices
Cisco is warning Unified Communications customers about NOT successfully offering support for Microsoft Windows 7
Cisco technical star Jonathan Rosenberg
Cisco will have no liability for any delay in delivery
Data Center
Douglas Smith - Cofounder and President of Network Instruments
Expand visibility of NetFlow-dependent NBAD and compliance applications
GigaStor captures and converts packets in NetFlow data flows
Index Venture partner Danny Rimer
Jonathan Rosenberg - a Cisco Fellow in Cisco's Voice Technology Group
Juniper MX960 lab test results
LANs / WANs
Mark Roberts - Polycom vice president of partner marketing
Michael Useem - Professor of Management
Microsoft
NetFlow
NetFlow add-ons
NetFlow overhead can overtax infrastructure
Network Behavior Anomaly Detection (NBAD)
Network Management
Non-NetFlow capable devices are blind to local traffic
Produce NetFlow about any device
SMB
Security
Selection committee member for America's Best Leaders
September 2009 vs. October 2009 Worldwide CCIE Count Comparison
Silver Lake Managing Director - Egon Durban
Skype's cofounders Niklas Zennstrom and Janus Friis
Software
The Charlie angle is to keep Dave Roux on track
The new Cisco ISR G2 portfolio is priced as follows
VoIP / Convergence
What are the benefits of GigaStor NetFlow Agent?
What’s new on the Cisco ISR G2 models vs. the old ISR models?
Windows 7
Windows 7 just not worth an all-out urgent effort by Cisco to support
Wireless / Mobile
eBay CEO - John Donahoe
sFlow
sFlow and NetFlow provides extended visibility
On The Web
Twitter