Queries: Is STP running On this router (not switch) on vlan 1

Router #show spanning-tree
VLAN1 is executing the ieee compatible Spanning Tree protocol
Bridge Identifier has priority 32768, address 4c4e.355f.e718
Configured hello time 2, max age 20, forward delay 15
We are the root of the spanning tree
Topology change flag not set, detected flag not set
Number of topology changes 14 last change occurred 1d21h ago
from FastEthernet0
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 0, notification 0, aging 300
Port 1 (FastEthernet0) of VLAN1 is forwarding
Port path cost 19, Port priority 128, Port Identifier 128.1.
Designated root has priority 32768, address 4c4e.355f.e718
Designated bridge has priority 32768, address 4c4e.355f.e718
Designated port id is 128.1, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
BPDU: sent 1072571, received 20

Router#show spanning-tree blockedports
Name Blocked Interfaces List

Number of blocked ports (segments) in the system : 0

Questions:

I dont understand. Why does it say spanning tree is enabled when there are no blocked ports.

Also I thought STP are supposed to run on switches. Why is the router giving such an output?

My topology consist of a router connected to a ring of 7 switches.

The topology works despite loopback occuring. I dont understand.

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Comments

networker050184

Your router has a switching module in it. STP does not have to block any ports if it is not needed.

Again, I'd strongly urge you to pick up a book and start reading the basics.

hitmen

hello moderator. Pls answer my questions. I understand spanning tree and I understand that in a spanning tree that there SHOULD be blocked ports.
However, this is not what I see in a real scenario.

Please explain instead of criticising me. How am I supposed to know that my router (L3) has a switching module that runs STP (should be in L2)? It is not in the textbook.

bermovick

hitmen wrote: »

We are the root of the spanning tree

If you understand spanning-tree, then explain why the root would ever have blocked ports.

FloOz

@Hitman a spanning tree root bridge has all of its ports in a forwarding (FWD) state. Your output clearly says that there are no ports that are blocking as well as saying "We are the root of the spanning tree"

Ivanjam

@hitmen - I cannot help but agree with networker050184 after seeing this question from you:

hitmen wrote: »

I dont understand. Why does it say spanning tree is enabled when there are no blocked ports.

After such as output (abbreviated):

hitmen wrote: »

Router #show spanning-tree
Bridge Identifier has priority 32768, address 4c4e.355f.e718
We are the root of the spanning tree
Designated root has priority 32768, address 4c4e.355f.e718

hitmen

Now I understand . I am only told about information on THIS router but not other devices. However this doesn't explain why an l3 router is running stp when it is supposed to be run on switches.

What is a switching module in a router? I haven't heard of it before.

NetworkVeteran

hitmen wrote: »

What is a switching module in a router? I haven't heard of it before.

When you Google switching module router, does anything helpful pop up?

Ivanjam

@hitmen - if you use Packet Tracer, try adding a NM-ESW-161 module to a 2811 router. You should explore the routers and modules in packet tracer if you use that program.

For reference, see: Cisco EtherSwitch Modules for the Integrated Services Routers [Cisco 2600 Series Multiservice Platforms] - Cisco Systems

Ivanjam

@hitmen - in case you are wondering why people seem to be a bit harsh in their responses to your queries, it may stem from the fact that you claim to be CCNA certified and yet you ask questions that all CCNA holders should know the answer to. Had you declared yourself a Cisco newbie, you most likely would have got much more measured and receptive responses.

hitmen

I know that the other 2 ports are designated ports. The problem is that I am a paper ccna but without actual experience.

Ivanjam

@hitmen - if the definition of "paper CCNA" is someone without production experience in networking, then the cap fits me too as I don't even work in IT as yet. However, I have a pretty large home lab by CCNA standards and I constantly use Packet Tracer and GNS3 to practice various topologies and commands, so I wouldn't say that I have zero experience. I encourage you to continue on your chosen path and don't be discouraged - read, watch videos, use GNS3/Packet Tracer/Boson etc to keep the material fresh in your head or else you will lose it, as any of the experienced guys here can tell you.