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Transparent bridge

Transparent bridge. CAM. Showing CAM table. Learning and ageing. Loops. STP and BPDUs. STP – key terms. Root switch election. Root switch election. STP – Port costs. STP – Root port selection. Convergence times. STP Enhancements .

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Transparent bridge

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  1. Transparent bridge

  2. CAM

  3. Showing CAM table

  4. Learning and ageing

  5. Loops

  6. STP and BPDUs

  7. STP – key terms

  8. Root switch election

  9. Root switch election

  10. STP – Port costs

  11. STP – Root port selection

  12. Convergence times

  13. STP Enhancements • Portfast. Excludes ports which are not connected to bridges or switches. Reduces the STP data size. Ports do not go through blocking, listening, learning and forwarding phases, but go straight to forwarding. If DHCP is required on a machine, Portfast is needed, as there will be a 30-50 delay as the port goes through the main phases. (config)# int fa0/1 (config-if)# spanning-tree portfast # sh running spanning-tree mode pvst no spanning-tree optimize bpdu transmission spanning-tree extend system-id ! ! interface FastEthernet0/1 no ip address spanning-tree portfast

  14. STP Enhancements # show spanning-tree summary Switch is in pvst mode Root bridge for: none EtherChannel misconfiguration guard is enabled Extended system ID is enabled Portfast is disabled by default PortFast BPDU Guard is disabled by default Portfast BPDU Filter is disabled by default Loopguard is disabled by default UplinkFast is disabled BackboneFast is disabled Pathcost method used is short Name Blocking Listening Learning Forwarding STP Active ---------------------- -------- --------- -------- ---------- ---------- VLAN0001 4 0 0 3 7 ---------------------- -------- --------- -------- ---------- ---------- 1 vlan 4 0 0 3 7 # show spanning int fa0/2 Vlan Role Sts Cost Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- VLAN0001 Altn BLK 19 128.2 P2p # sh spanning int fa0/3 Vlan Role Sts Cost Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- VLAN0001 Desg FWD 19 128.3 P2p • Portfast. Excludes ports which are not connected to bridges or switches. Reduces the STP data size. Ports do not go through blocking, listening, learning and forwarding phases, but go straight to forwarding. If DHCP is required on a machine, Portfast is needed, as there will be a 30-50 delay as the port goes through the main phases.

  15. STP Enhancements • BPDU Guard. Shuts down the port when it receives a BPDU, and goes into an error disable state. Switch(config-if)# spanning ? bpdufilter Don't send or receive BPDUs on this interface bpduguard Don't accept BPDUs on this interface cost Change an interface's spanning tree port path cost guard Change an interface's spanning tree guard mode link-type Specify a link type for spanning tree protocol use mst Multiple spanning tree port-priority Change an interface's spanning tree port priority portfast Enable an interface to move directly to forwarding on link up stack-port Enable stack port vlan VLAN Switch Spanning Tree Switch(config-if)# spanning bpduguard ? disable Disable BPDU guard for this interface enable Enable BPDU guard for this interface Switch(config-if)#spanning bpduguard enable Switch(config-if)# 00:17:16: %SPANTREE-2-BLOCK_BPDUGUARD: Received BPDU on port FastEthernet0/1 with BPDU Guard enabled. Disabling port.

  16. STP Enhancements • BPDU Filter. Filters BPDU packets on a port of a switch. If it receives more than 10 BPDU packets is disables PortFast, and returns to normal. Switch(config)#int fa0/1 Switch(config-if)#spanning ? bpdufilter Don't send or receive BPDUs on this interface bpduguard Don't accept BPDUs on this interface cost Change an interface's spanning tree port path cost guard Change an interface's spanning tree guard mode link-type Specify a link type for spanning tree protocol use mst Multiple spanning tree port-priority Change an interface's spanning tree port priority portfast Enable an interface to move directly to forwarding on link up stack-port Enable stack port vlan VLAN Switch Spanning Tree Switch(config-if)#spanning portfast ? disable Disable portfast for this interface trunk Enable portfast on the interface even in trunk mode <cr> Switch(config-if)#spanning bpduf ? disable Disable BPDU filtering for this interface enable Enable BPDU filtering for this interface Switch(config-if)#spanning bpduf enable

  17. STP Enhancements - Uplinks • Uplink. Uses a redundant link connection to reduce the convergence time to less than 4 seconds. Required: • Uplink enabled. • One port in a blocking state (on alternative path). • Failure is on the current switch. Switch(config)# sp ? backbonefast Enable BackboneFast Feature etherchannel Spanning tree etherchannel specific configuration extend Spanning Tree 802.1t extensions logging Enable Spanning tree logging loopguard Spanning tree loopguard options mode Spanning tree operating mode mst Multiple spanning tree configuration pathcost Spanning tree pathcost options portfast Spanning tree portfast options transmit STP transmit parameters uplinkfast Enable UplinkFast Feature vlan VLAN Switch Spanning Tree

  18. STP Enhancements - RSTP • Rapid STP (RSTP). 802.1W allows rapid convergence. Standard on many devices. PVST+ used on ISL or 802.1Q links to allow RSTP to work correctly – defined as RPVST+ (enabled by default). • RSTP can converge the spanning-tree instance in less than a second, as apposed to almost 50 seconds for standard 802.1D spanning tree). This type of setup is important in real-time applications such as voice and video traffic.

  19. STP Enhancements - MST • Multiple Spanning Tree (MST). MSTP (Multiple STP – IEEE 802.1S) are used to provide rapid convergence of the spanning-tree protocol. MSTP is used to group VLANs into a single spanning-tree instance. It allows multiple instances of STP, and reduce overhead time for PVST. Advantages: Load balancing and redundant connections. Disadvantages: more complex that standard, and more skill required. MST defines regions, and each switch has the same region name, the same revision number and the same VLAN table content. (config)# spanning-tree ? backbonefast Enable BackboneFast Feature etherchannel Spanning tree etherchannel specific configuration extend Spanning Tree 802.1t extensions loopguard Spanning tree loopguard options mode Spanning tree operating mode mst Multiple spanning tree configuration pathcost Spanning tree pathcost options portfast Spanning tree portfast options uplinkfast Enable UplinkFast Feature vlan VLAN Switch Spanning Tree (config)# spanning-tree mst ? WORD MST instance range, example: 0-3,5,7-9 configuration Enter MST configuration submode forward-time Set the forward delay for the spanning tree hello-time Set the hello interval for the spanning tree max-age Set the max age interval for the spanning tree max-hops Set the max hops value for the spanning tree (config)# spanning-tree mst configuration

  20. STP Enhancements - MST (config)# spanning-tree mst configuration (config-mst)# ? abort Exit region configuration mode, aborting changes exit Exit region configuration mode, applying changes instance Map vlans to an MST instance name Set configuration name no Negate a command or set its defaults private-vlan Set private-vlan synchronization revision Set configuration revision number show Display region configurations (config-mst)# instance ? <0-15> MST instance id (config-mst)# instance 1 ? vlan Range of vlans to add to the instance mapping (config-mst)# instance 1 vlan ? LINE vlan range ex: 1-65, 72, 300 -200 (config-mst)# instance 1 vlan 1 (config-mst)# name ? WORD Configuration name (config-mst)# name fred (config-mst)# revision ? <0-65535> Configuration revision number (config-mst)# revision 1 (config-mst)# exit (config)# spanning-tree mode ? mst Multiple spanning tree mode pvst Per-Vlan spanning tree mode rapid-pvst Per-Vlan rapid spanning tree mode (config)# spanning-tree mode mst • Multiple Spanning Tree (MST). Allows multiple instances of STP, and reduce overhead time for PVST. Advantages: Load balancing and redundant connections. Disadvantages: more complex that standard, and more skill required. • MST defines regions, and each switch has the same region name, the same revision number and the same VLAN table content.

  21. STP Enhancements - Etherchannels (config)# lacp ? system-priority LACP priority for the system (config)# lacp system-priority ? <1-65535> Priority value (config)# lacp system-priority 2 (config)# interface fa0/1 (config-if)# channel-protocol ? lacp Prepare interface for LACP protocol pagp Prepare interface for PAgP protocol (config-if)# channel-protocol lacp (config-if)# channel-group ? <1-6> Channel group number (config-if)# channel-group 1 ? mode Etherchannel Mode of the interface (config-if)# channel-group 1 mode ? active Enable LACP unconditionally auto Enable PAgP only if a PAgP device is detected desirable Enable PAgP unconditionally on Enable Etherchannel only passive Enable LACP only if a LACP device is detected (config-if)# channel-group 1 mode active (config-if)# lacp ? port-priority LACP priority on this interface (config-if)# lacp port-priority ? <1-65535> Priority value (config-if)# lacp port-priority 1 • Etherchannels allow ports to aggregated to be treated as a single channel. They use LACP (Link Aggregation Control Protocol - IEEE 802.3ad). The LACP packets use EtherChannels to intercommunicate, where the neighours and and port group capabilities are learnt and compared with local switch capabilities. In LACP there are roles assigned to the EtherChannel endpoints. Thus the switch with the lowest system priority is then elected to make decisions about what ports are actively participating in the EtherChannel.

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