I want to ask whether all the user traffic goes through root switch. If there is redundant link available stp (Spanning Tree Protocol) block that link for loop prevention. So there is no option left the traffic will go through the other way only which is left. But you said that no traffic goes through root switch.
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This question is a bit confusing. First of all, I'm assuming you're talking about Spanning Tree Protocol or STP?– Todd WilcoxCommented Jul 23, 2015 at 19:17
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@Mohd, Can you create a diagram? That would help a discussion.– Ron TrunkCommented Jul 23, 2015 at 19:24
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Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.– Ron Maupin ♦Commented Aug 12, 2017 at 3:51
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3 Answers
Depending on topology and endpoints, user traffic does not need to traverse the root bridge (eg: two endpoints on the same or adjacent switches that is/are not the root bridge).
The root bridge is however the basis for which the active link between all bridges is determined.
See Per-VLAN Spanning Tree (PVST) and Per-VLAN Spanning Tree Plus (PVST+). This would allow you send some traffic across the redundant layer 2 link.
NOTES:
Spanning Tree Protocol - (IEEE)
802.1D STP (Spanning Tree Protocol)
801.1s MSTP (Multiple Spanning Trees Protocol)
802.1w RSTP (Rapid Spanning Tree Protocol)
Permits only a single path toward the root bridge
Is outdated, replaced by 802.1q-2014(.aq Shortest Path Bridging, SPB)
Path Cost determined by the access speeds of the links determine the path cost
* Don't Deploy STP
MLAG Multi-Chassis Link Aggregation Groups
VSS
Cross-Stack Etherchannel
FabricPath (uses IS-IS at layer 2)
VPC (Virtual Port Channel)
Brocade’s VCS (Virtual Cluster Switching)
IETF TRILL (Transparent Interconnection of Lots of Links)
IEEE 802.1aq (Shortest Path Bridging – SPB)
answered Jul 24, 2015 at 16:58
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1Only applies if using Cisco, although a number of other vendors have a similar proprietary STP implementation.– YLearnCommented Aug 2, 2015 at 13:27
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MSTP (standards based) also allows redundant links to be utilised by a subset of VLANs. Each MSTI has it's own topology and root bridge. Commented Oct 12, 2015 at 5:27
It's not necessarily true all user traffic will go through the root before reaching its destination.
Each switch or vlan will just have one best path to get to the root. If you set is up and look at each path you will see where the "tree" comes from in STP.
