BCP Support

The Bridge Control Protocol (BCP) Support feature provides support for BCP to Cisco devices, as described in RFC 3518. The Cisco implementation of BCP is a VLAN infrastructure that does not require the use of subinterfaces to group Ethernet 802.1Q trunks and the corresponding PPP links. This approach enables users to process VLAN encapsulated packets without having to configure subinterfaces for every possible VLAN configuration.

Feature History for the BCP Support feature

Release
Modification

12.3(2)T

This feature was introduced.

12.3(4)T

This feature was modified to enhance the performance of the bridging of Ethernet packets over PPP-encapsulated interfaces. The ppp bcp tagged-frame command was introduced to provide the option to either enable or disable the negotiation of IEEE 802.1Q-tagged packets.


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Contents

•Restrictions for BCP Support

•Information About BCP Support

•How to Bridge a Range of VLAN IDs

•Configuration Examples for BCP Support

•Additional References

•Command Reference

Restrictions for BCP Support

Each individual VLAN ID can be configured only once, as either part of a single VLAN ID range or on a subinterface.

Information About BCP Support

To configure the BCP Support feature, you must understand the following concept:

•VLAN ID Ranges

VLAN ID Ranges

In the traditional, subinterface-based approach to VLANs, a subinterface is created for every necessary VLAN ID, and then the application or protocol attributes are configured on every subinterface. In the VLAN range approach, a single VLAN ID range is created, and the application or protocol attributes are configured on the range as a whole.

How to Bridge a Range of VLAN IDs

This section contains the following procedures:

•Configuring a Range of VLAN IDs

•Enabling the Negotiation of IEEE 802.1Q-Tagged Packets

Configuring a Range of VLAN IDs

In this task, you create a range of VLAN IDs and then assign the VLAN ID range to the serial interface.

SUMMARY STEPS

1. enable

2. configure terminal

3. no ip routing

4. bridge number protocol ieee

5. interface type number

6. vlan-range dot1q start-range end-range [native]

7. description description

8. bridge-group number

9. exit

10. interface type number

11. encapsulation ppp

12. bridge-group number

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router(config)# enable

Enters privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Router(config)# configure terminal

Enters global configuration mode.

Step 3 

no ip routing

Example:

Router(config)# no ip routing

Disables all routing.

Step 4 

bridge number protocol ieee

Example:

Router(config)# bridge 1 protocol ieee

Enables bridge and spanning-tree protocols.

Step 5 

interface type number

Example:

Router(config)# interface ethernet 0

Enters interface configuration mode.

•This is the Ethernet interface that is connected to the 802.1Q trunk. Both the Ethernet interface and the serial interface must be assigned to the same bridge group.

Step 6 

vlan-range dot1q start-range end-range [native]

Example:

Router(config-if)# vlan-range dot1q 1 99

Configures the range of VLAN IDs the interface is to bridge and enters VLAN range configuration mode.

•Configuring the native keyword instructs the interface to bridge untagged (native) packets.

Step 7 

description description

Example:

Router(config-if-vlan-range)# description 1 to 99

(Optional) Describes the VLAN ID range.

Step 8 

bridge-group number

Example:

Router(config-if-vlan-range)# bridge-group 1

Assigns the VLAN ID range to a bridge group.

Step 9 

exit

Example:

Router(config-if-vlan-range)# exit

Exits to global configuration mode.

Step 10 

interface type number

Example:

Router(config)# interface serial 1

Enters interface configuration mode.

Step 11 

encapsulation ppp

Example:

Router(config-if)# encapsulation ppp

Enables PPP on the interface.

Step 12 

bridge-group number

Example:

Router(config-if)# bridge-group 1

Assigns the interface to a bridge group.

•The serial interface must be assigned to the same bridge group as the Ethernet interface that is connected to the 802.1Q trunk.

Enabling the Negotiation of IEEE 802.1Q-Tagged Packets

In this task, you enable the negotiation of IEEE 802.1Q-tagged packets.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface type number

4. ppp bcp tagged-frame

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router(config)# enable

Enters privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router(config)# configure terminal

Enters global configuration mode.

Step 3 

interface type number

Example:

Router(config)# interface serial 4/0

Enters interface configuration mode.

•This is the interface that will be bridging the IEEE 802.1Q-tagged packets.

Step 4 

ppp bcp tagged-frame

Example:

Router(config-if)# ppp bcp tagged-frame

Enables the negotiation of IEEE 802.1Q-tagged packets.

Configuration Examples for BCP Support

This section provides the following configuration examples:

•Bridging a Range of VLAN IDs: Example

•Bridging a Range of VLAN IDs over Multiple Interfaces: Example

•Bridging a Range of VLAN IDs from Untagged Packets: Example

•Enabling the Negotiation of IEEE 802.1Q-Tagged Packets: Example

Bridging a Range of VLAN IDs: Example

The following example bridges tagged 802.1Q packets that have VLAN IDs from 1 to 500. Ingress packets that have VLAN IDs outside of this range are dropped. 

no ip routing

!

bridge 1 protocol ieee

!

interface ethernet 0

 vlan-range dot1q 1 500

  bridge-group 1

!

interface serial 0

 encapsulation ppp

 bridge-group 1

Bridging a Range of VLAN IDs over Multiple Interfaces: Example

The following example bridges two ranges of VLAN IDs. Packets with a VLAN ID from 1 to 600 are bridged by serial interface 0, and packets with a VLAN ID from 800 to 4000 are bridged by serial interface 1. 

no ip routing

!

bridge 1 protocol ieee

bridge 2 protocol ieee

!

interface ethernet 0

 vlan-range dot1q 1 600

  bridge-group 1

 vlan-range dot1q 800 4000

  bridge-group 2

!

interface serial 0

 encapsulation ppp

 bridge-group 1

!

interface serial 1

 encapsulation ppp

 bridge-group 2

Bridging a Range of VLAN IDs from Untagged Packets: Example

The following example bridges untagged packets with a VLAN ID from 1 to 500: 

interface ethernet 0

 vlan-range dot1q 1 500 native

  bridge-group 1

Enabling the Negotiation of IEEE 802.1Q-Tagged Packets: Example

The following example enables the negotiation of IEEE 802.1Q-tagged packets on serial interface 4/0: 

interface serial 4/0

 ppp bcp tagged-frame

Additional References

The following sections provide references related to BCP support:

RFCs

RFCs
Title

3518

Point-to-Point Protocol (PPP) Bridging Control Protocol (BCP)

2878

Point-to-Point Protocol (PPP) Bridging Control Protocol (BCP)

1638

PPP Bridging Control Protocol (BCP)


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Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Bridging Command Reference at http://www.cisco.com/en/US/docs/ios/bridging/command/reference/br_book.html or the Cisco IOS IBM Networking Command Reference at http://www.cisco.com/en/US/docs/ios/ibm/command/reference/ibm_book.html. For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List.

New Commands

•debug tbridge virtual-port

•ppp bcp tagged-frame

•vlan-id dot1q

•vlan-range dot1q

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