8 votes
Accepted

Two switches, double connection, no LACP: how does it work?

Most likely, the rapid or the multiple spanning tree protocol RSTP/MSTP has been activated on the 1910 switch. With the unmanaged 1410 switch forwarding STP BPDUs (most do), the 1910 notices a loop to ...
Zac67's user avatar
  • 84.4k
7 votes

Two switches, double connection, no LACP: how does it work?

Most switches comes with Spanning Tree (STP) enabled by default. This protocols will detect the loop and disable one of the link to break it. The new switch you connect either has STP disabled or a ...
JFL's user avatar
  • 19.7k
3 votes

Spanning Tree Protocol - Redundant Links

S3 port F 0/2 is in the blocking state. So it won't receive frames from S2. Traffic from S2 to S3 has to go through S1.
Ron Trunk's user avatar
  • 67.5k
3 votes
Accepted

STP related question

Disabling STP and creating a loop will crash the network with a broadcast storm. STP was designed to prevent layer-2 loops by enabling a single loop-free path to the root bridge. STP is communicated ...
Ron Maupin's user avatar
  • 99.6k
2 votes

How does STP technically generate the path cost for an interface?

You are using obsolete interface metrics from classic STP (IEEE 802.1D-1998). Current versions are RSTP and MSTP which use the standard metric 20 Tbit/s divided by link rate - which simplifies ...
Zac67's user avatar
  • 84.4k
2 votes
Accepted

how can a STP switch time out MAC addresses from the table in Listening state?

A switch can have learned MACs from other interfaces. So when a blocked port transitions to listening, there are already MAC addresses in the table and any MACs received on the listening port won't ...
Ron Trunk's user avatar
  • 67.5k
2 votes

In STP, how does a switch know that a peer port is blocked?

Usually the lower port ID (for same link metric) takes precedence, so most likely Fa0/24 would be blocked. The algorithm runs like that: Cat2 recognizes Cat1 as root bridge on Fa0/23 and Fa0/24. It ...
Zac67's user avatar
  • 84.4k
1 vote

STP related question

xSTP relies on passing BPDUs between switch ports. Managed switches don't usually forward those frames (as it should be), so a managed switch without STP in between two others with STP active breaks ...
Zac67's user avatar
  • 84.4k
1 vote
Accepted

Spanning Tree Protocol - Redundant Links

You are thinking in terms of direct point to point links between spanning-tree capable switches. That is the most common case in networks today, but it's not the only case to consider. In general an ...
Peter Green's user avatar
  • 13.3k
1 vote

RSTP convergence of p2p links

For RSTP, won't all the links move to forwarding state immediately since they are all p2p links? No. A (non-edge) RSTP port will only be "rapid" if negotiation (a.k.a. Proposal & ...
Marc 'netztier' Luethi's user avatar
1 vote
Accepted

Juniper EX bpdu-timeout-action not blocking interface

The BPDU-timeout action only takes effect when BPDUs have been received on a port and THEN they time out - so the port will need to be root or backup/alternate for it to work. I don't think you'll be ...
Benjamin Dale's user avatar

Only top scored, non community-wiki answers of a minimum length are eligible