Fundamentos Satelite

SPANNING TREE · PART 1 packetlife.net
Spanning Tree Protocols
Legacy STP PVST PVST+ RSTP RPVST+ MST
Algorithm Legacy ST Legacy ST Legacy ST Rapid ST Rapid ST Rapid ST
Definition 802.1D-1998 CiscoCisco 802.1w,
802.1D-2004
Cisco 802.1s,
802.1Q-2003
Instances One Per VLAN Per VLAN One Per VLAN Configurable
Trunking N/A ISL 802.1Q, ISL N/A 802.1Q, ISL 802.1Q, ISL
Spanning Tree InstanceComparison
BPDU Format
Field Bits
Protocol ID 16
Version 8
BPDU Type 8
Flags 8
Root ID 64
Root Path Cost 32
Bridge ID 64
Port ID 16
Message Age 16
Max Age 16
Hello Time 16
Forward Delay 16Default Timers
Hello 2s
Forward Delay 15s
Max Age 20s
Spanning Tree Specifications
Open Standards
IEEE 802.1D-1998 · Deprecated legacy STP standard
IEEE 802.1w · Introduced Rapid STP (RSTP)IEEE 802.1D-2004 · Replaced legacy STP with RSTP
IEEE 802.1s · Introduced Multiple Spanning Tree (MST)
IEEE 802.1Q-2003 · Added MST to 802.1Q
Cisco Proprietary Implementations
PVST · Per-VLANimplementation of legacy STP
PVST+ · Added 802.1Q trunking to PVST
RPVST+ · Per-VLAN implementation of RSTP
Link Costs
Bandwidth Cost
4 Mbps 250
10 Mbps 100
16 Mbps 62
45 Mbps 39
100 Mbps 19
155Mbps 14
622 Mbps 6
1 Gbps 4
10 Gbps 2
Port States
Legacy ST Rapid ST
Disabled Discarding
Blocking Discarding
Listening Discarding
Learning Learning
Forwarding Forwarding
Spanning TreeOperation
1 Determine root bridge The bridge advertising the lowest bridge ID becomes
the root bridge
2 Select root port Each bridge selects its primary port facing the root
3 Select designated portsOne designated port is selected per segment
4 Block ports with loops All non-root and non-desginated ports are blocked
Port Roles
Legacy ST Rapid ST
Root Root
Designated Designated
BlockingAlternate
Blocking Backup
by Jeremy Stretch v2.0
SPANNING TREE · PART 2 packetlife.net
PVST+ and RPVST+ Configuration
! Set STP type
spanning-tree mode {pvst | rapid-pvst}
! Bridge priority...