17

In the spanning tree algorithm the process of determining the root bridge is based on the bridge priority (BID). When there were no VLANs (meaning that switches had to deal with only one broadcast domain) the BID was equal to: Bridge priority - MAC Address <2 bytes> <6 bytes> As Network administrators we can modify the bridge priority ...


14

First, like the others have mentioned you have no bridging loop here due to running a Portchannel. That said, running STP is still fine. Let me clear some confusions on how these commands work on Cisco switches. spanning-tree portfast trunk This command is supposed to be run on trunk ports towards non bridging devices, such as a server with multiple VLANs ...


12

You really, really do not want to disable STP where you connect switches to other switches. That is the entire purpose of STP. If you disable STP, and there is a problem, it will really be too late because your entire network could crash when you notice it, and recovering from a broadcast storm is no fun at all. By the way, portfast doesn't actually disable ...


11

RSTP needs backwards compatibility with STP switches. Thus Discarding state merges Disabled, Blocking, Listening into one. Ideally if running a complete RSTP topology then discarding becomes practically unneeded due to the explanation below. In STP BPDU will only be sent from root bridge > down, therefore non-root bridges would only forward on BPDUs that ...


10

Layer 3 (mostly IP) generally relies on the underlying layer-2 network (mostly Ethernet or Wi-Fi) for delivery. Just like a layer-2 network uses layer-1 links to actually move the bits. The difference in moving data at layer 1, 2 or 3 is the complexity of the devices. Layer-1 devices (repeaters) just copied bits - simple, yet inefficient and long obsolete. ...


9

The bridge ID is an 8-Byte (64 bit) value composed of the following elements: The bridge priority value and the system ID extension together make up a 16 bit (2-byte) value. The bridge priority value, making up the left most bits, is a value of 0 to 61440. The extended system ID is a value of 1 to 4095 corresponding to the respective VLAN participating in ...


9

802.1D STP has configuration BPDUs sent by the root bridge. The designated bridges relay these BPDUs on their designated ports. All BPDUs flow from the root. With 802.1D, a port going up or down will generate a topology change, unless portfast has been configured on the port. When a switch detects a topology change it will generate a TCN BPDU, which is a ...


9

you need to understand the next Spanning-Tree Port Roles - Root Port (RP) - It is a port on a non-root switch, which is the shortest (the best) path towards the root bridge. (i.e. port 0/4 0/3 in SW3) - Designated Port (DP) - It is a port that is in the forwarding state. (i.e. port 0/1 0/2 SW2) - Non-Designated Port (NDP) - It is a port that is in a ...


9

Great question! This is because a layer-2 switching loop can form on the Consumer-grade switching equipment which could produce Broadcast Radiation and impact devices connected to the broadcast domain. STP was originally standardized as IEEE 802.1D. Its purpose is to build loop-free, layer 2 typologies. STP does not detect and then mitigate Broadcast ...


9

To add to Zac67's and JFL's answers: In case you decide to enable spanning-tree on the single switch, don't forget to configure the client's and server's switchports as Edge Ports (Cisco speak; spanning-tree portfast [trunk], spanning-tree portfast edge [trunk] or spanning-tree port type egde [trunk] , depending on platform and software generation). This ...


9

MSTP and RSTP converge equally fast, MSTP is the current protocol version. Given the topology in your diagram (ugh!) and its tree depth, no STP variant will converge quickly (if at all). xSTP default parameters are designed for a maximum tree depth or chain length of 20 hops. Building longer/deeper constructs requires parameter tuning or your network will ...


8

Spanning tree only runs between switches, never to standard end hosts. Bear in mind that, under normal circumstances, a port supporting spanning tree will (when it first comes up) run through a sequence of first listening for BPDU's, then learning source addresses and then finally forwarding frames. This can take ~30 seconds, during which the connected ...


8

Strongly suggested: Configure both port-channel and its members identically (except of course for description and the channel-group and vpc bits). As long as an interface is not configured to be member of a LAG, or because LACP negotiation failed and the interface remains LACP individual [1], the configuration from the given (physical) interface applies, ...


7

I don't think it's possible to give a definitive answer on this because it will depend on the switch architecture, CPU power, the distance between the switches, the topology, the speed of the links and so on. I assume the delay would be something like this if we have three switches daisy chained: +----------+ +----------+ +----------+ | ...


7

The short answer is, your proposed additional fiber in the diagram will not gain you any real advantage for VLAN 3. All traffic from Packaging or Fiberglass, destined to the server in Shipping on VLAN 3, will still traverse the Core. (Presuming that you have already properly tuned your Spanning Tree settings to make the Core switch stack the root bridge.) ...


7

Found the answer: show spanning-tree interface INT detail This command goes deeper than the regular "show spanning-tree" and displays the designated bridge as well as root bridge.


7

If i remember, default spanning tree (802.1d) takes about 50 secs to reconverge. That is the duration for which you will be losing frames. A link is detected down by the loss of 10 hello pkts. These are usually 2 secs apart. So total=20 secs. This is called the max-age timer Next it has to transition another blocked port through listening and learning ...


7

Some corrections to the above answer. Port-id and port-priority are different. One is configurable. The other is internally set. I'll make an attempt to answer your question below. There has to be just 1 root port per switch. By definition , this is the port with the lowest path-cost to root. A path-cost is the sum of all port-costs along a given path. ...


7

That will depend on the switch vendor, switch model, and software version which the switch is running. When a new standard emerges, it can take some vendors a while to update their code to support the new standard. If there are switch model which the vendor no longer supports, they may never be able to support the new standard. The default STP version for ...


7

Now what exactly are the CST, the IST, and the CIST? Can someone draw me a simple MSTP topology with CST in red, IST in yellow, and CIST in green, so as to have a final reference without any ambiguous texts to be interpreted? :) I like to visualise them like this:


7

Yes it did make him go through a more costly path. Maybe you aren't confused on how it works, maybe you're confused on what it's for? Spanning-tree is for stopping network loops. It finds short paths from the root to each edge, and closes other paths between edges - it's not about making every connection as short as possible. Consider your picture - you ...


7

You have a fundamental problem with your configuration, which is that the configuration digests on core and access switches don't match. [Core-sw]dis stp region-configuration Oper Configuration Format selector : 0 Region name : ***edited*** Revision level : 0 Configuration digest : 0x950fe4b63ba3d47dc4a539d00f613bb9 ...


7

(R)PVST(+) is a proprietary standard defined by Cisco (or a set thereof). However, there are many other vendors and devices supporting it - you may need to check the specifications of your devices. The IEEE standard alternative is MSTP which enables separate spanning trees for different MSTP instances. Additionally, MSTP also supports splitting a network ...


7

The basic function of a switch is transparent bridging - for this, it doesn't need any MAC address of its own. However, if you need to talk to a switch - ie. a managed switch - then that switch requires an address; usually that is a MAC address and an IP address [*]. STP is only supported on managed switches and in addition, an STP bridge is required to have ...


7

If you can use Cisco Metro Ethernet switches, you might consider Resilient Ethernet Protocol, which is designed for ring topologies. REP is a protocol used in order to replace the Spanning Tree Protocol (STP) in some specific Layer 2 network designs. ... Benefits Here are some of the benefits of REP: REP offers these convergence times: ...


7

Generally, a ring is a bad design for Ethernet switches. STP blocks one of the ring links, forming a chain. Traffic between switches on opposite sides need to cross the whole chain, potentially causing link congestion. In your diagram with A being the root switch, C-to-D traffic would require four L2 hops. With 802.1D-compliant switches/bridges, STP BPDUs ...


6

On a general note: not everything that is present in parser, will actually work on given platform, or even makes sense. In that particular case, you can enable spanning tree if you have either IRB (integrated routing & bridging) configured on ethernet ports, or you insert the integrated switching module (WIC-4ESW) into the router. Then, those ports are ...


6

The ME3600s don't support the forwarding of STP or MST frames through EVC. Port based PWE3s will transport STP frames but you will have to chew up a lot of ports. Really you should be engaging your vendor to platform specific questions like this that are "Will the switch support X feature" or "Does your switch forward X traffic". I suggest also habinga look ...


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