Table Of Contents

Configuring Bridging on the ML-Series Card

Understanding Bridging

Configuring Bridging

Monitoring and Verifying Bridging

Configuring Bridging on the ML-Series Card

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This chapter describes how to configure bridging for the ML-Series card. Bridging is one of the simplest configurations of the ML-Series card. Other alternatives exist to simple bridging, such as Integrated Routing and Bridging (IRB). The user should consult the chapter detailing their desired type of configuration.

This chapter includes the following major sections:

•Understanding Bridging

•Configuring Bridging

•Monitoring and Verifying Bridging

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Caution Cisco Inter-Switch Link (ISL) and Cisco Dynamic Trunking Protocol (DTP) are not supported by the ML-Series cards, but the ML-Series broadcast forwards these formats. Using ISL or DTP on connecting devices is not recommended. Some Cisco devices attempt to use ISL or DTP by default.

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Understanding Bridging

The ML-Series card supports transparent bridging for Fast Ethernet, Fast EtherChannel (FEC), POS ports and POS channel. It supports a maximum of 255 active bridge groups. Transparent bridging combines the speed and protocol transparency of a spanning-tree bridge, along with the functionality, reliability, and security of a router.

To configure bridging, you must perform the following tasks in the modes indicated:

•In global configuration mode:

–Enable bridging of IP packets.

–Select the type of Spanning Tree Protocol (STP) (optional).

•In interface configuration mode:

–Determine which interfaces belong to the same bridge group.

The ML-Series card bridges all nonrouted traffic among the network interfaces comprising the bridge group. If spanning tree is enabled, the interfaces became part of the same spanning tree. Interfaces not participating in a bridge group cannot forward bridged traffic.

If the destination address of the packet is known in the bridge table, the packet is forwarded on a single interface in the bridge group. If the packet's destination is unknown in the bridge table, the packet is flooded on all forwarding interfaces in the bridge group. The bridge places source addresses in the bridge table as it learns them during the process of bridging.

Spanning tree is not mandatory for an ML-Series card bridge group. But if it is configured, a separate spanning-tree process runs for each configured bridge group. A bridge group establishes a spanning tree based on the bridge protocol data units (BPDUs) it receives on only its member interfaces. The ML-Series card has a 255 active bridge group maximum.

Configuring Bridging

Beginning in global configuration mode, use the following steps to configure bridging:

	Command	Purpose
Step 1	ML_Series(config)# no ip routing	Enables bridging of IP packets. This command needs to be executed once per card, not once per bridge-group. This step is not done for IRB.
Step 2	ML_Series(config)# bridge bridge-group-number [protocol {drpi-rstp | rstp | ieee}]	Assigns a bridge group number and defines the appropriate spanning-tree type: drpri-rstp is the protocol used to interconnect dual RPR to protect from node failure. Do not configure this option on the ONS 15310-CL ML-Series. rstp is the IEEE 802.1W Rapid Spanning Tree. ieee is the IEEE 802.1D Spanning Tree Protocol . Note Spanning tree is not mandatory for an ML-Series card bridge group. But configuring spanning tree blocks network loops.
Step 3	ML_Series(config)# bridge bridge-group-number priority number	(Optional) Assigns a specific priority to the bridge, to assist in the spanning-tree root definition. Lowering the priority of a bridge makes it more likely the bridge is selected as the root.
Step 4	ML_Series(config)# interface type number	Enters interface configuration mode to configure the interface of the ML-Series card.
Step 5	ML_Series(config-if)# bridge-group bridge-group-number	Assigns a network interface to a bridge group.
Step 6	ML_Series(config-if)# no shutdown	Changes the shutdown state to up and enables the interface.
Step 7	ML_Series(config-if)# end	Returns to privileged EXEC mode.
Step 8	ML_Series# copy running-config startup-config	(Optional) Saves your entries in the configuration file.

Figure 4-1 shows a bridging example. Example 4-1 shows the code used to configure ML-Series A. Example 4-2 shows the code used to configure ML-Series B.

Figure 4-1 Bridging Example

Example 4-1 ML_Series A Configuration

bridge irb

bridge 1 protocol ieee

!

!

interface FastEthernet0

 no ip address

 bridge-group 1

!

interface POS0

 no ip address

bridge-group 1

Example 4-2 ML_Series B Configuration

bridge irb

bridge 1 protocol ieee

!

!

interface FastEthernet0

 no ip address

 bridge-group 1

!

interface POS0

 no ip address

bridge-group 1

Monitoring and Verifying Bridging

After you have set up the ML-Series card for bridging, you can monitor and verify its operation by performing the following procedure in privileged EXEC mode:

	Command	Purpose
Step 1	ML_Series# clear bridge bridge-group-number	Removes any learned entries from the forwarding database of a particular bridge group, clears the transmit, and receives counts for any statically configured forwarding entries.
Step 2	ML_Series# show bridge {bridge-group-number | interface-address}	Displays classes of entries in the bridge forwarding database.
Step 3	ML_Series# show bridge verbose	Displays detailed information about configured bridge groups.
Step 4	ML_Series# show spanning-tree [bridge-group-number][brief]	Displays detailed information about spanning tree. bridge-group-number restricts the spanning tree information to specific bridge groups. brief displays summary information about spanning tree.

Example 4-3 shows examples of monitoring and verifying bridging.

Example 4-3 Monitoring and Verifying Bridging

ML_Series# show bridge 1

Total of 1260 station blocks, 310 free

Codes: P - permanent, S - self

Bridge Group 1:

Maximum dynamic entries allowed: 1000

Current dynamic entry count: 1

    Address       Action   Interface

0000.0001.3100   forward   FastEthernet0

ML_Series# show spanning-tree 1

Bridge group 1 is executing the rstp compatible Spanning Tree protocol

  Bridge Identifier has priority 32768, sysid 1, address 000b.fcfa.339e

  Configured hello time 2, max age 20, forward delay 15

  We are the root of the spanning tree

  Topology change flag not set, detected flag not set

  Number of topology changes 1 last change occurred 1w1d ago

          from POS0.1

  Times:  hold 1, topology change 35, notification 2

          hello 2, max age 20, forward delay 15

  Timers: hello 0, topology change 0, notification 0, aging 300

 Port 3 (FastEthernet0) of Bridge group 1 is designated disabled

   Port path cost 19, Port priority 128, Port Identifier 128.3.

   Designated root has priority 32769, address 000b.fcfa.339e

   Designated bridge has priority 32769, address 000b.fcfa.339e

   Designated port id is 128.3, designated path cost 0

   Timers: message age 0, forward delay 0, hold 0

   Number of transitions to forwarding state: 0

   Link type is point-to-point by default

   BPDU: sent 0, received 0

 Port 15 (POS0.1) of Bridge group 1 is designated down

   Port path cost 37, Port priority 128, Port Identifier 128.15.

   Designated root has priority 32769, address 000b.fcfa.339e

   Designated bridge has priority 32769, address 000b.fcfa.339e

   Designated port id is 128.15, designated path cost 0

   Timers: message age 0, forward delay 0, hold 0

   Number of transitions to forwarding state: 1

   Link type is point-to-point by default

   BPDU: sent 370832, received 4