Spanning Tree question

agustinchernitsky

Hi all... Just a quick one regarding Root Ports. Imagine this network:

[SW D]----------[SW E]
    |             |
    |             |
[SW C]         [SW B]
    |             |
[ Root Bridge SW A ]

SW D-E: 1 GBps
SW D-C: 1 GBps
SW E-B: 100 MBps
SW C-A: 100 MBps
SW B-A: 100 MBps

STA would create this topology (correct me here please):

1.- All SW A will be in Designated ports (DP)
2.- SW B port to SW A will be Root Port (RP)
3.- SW C port to SW A will be RP
4.- SW B port to SW E will be DP but SW E port to SW B will be blocked
5.- SW E port to SW D port will be RP and DP respectivly
6.- SW D port to SW C port will be RP and DP respectivly

Is this correct? I think that frames should go from E to D and the C because of the cost of the path (4 + 4 + 19). Is this correct?

Thanks Amigos!

hankooknara

I agree on all of it.. Someone can correct us I guess

1.- All SW A will be in Designated ports (DP)
correct(although not sure if root bridge's ports are also called DP(fits the definition).
2.- SW B port to SW A will be Root Port (RP)
agree
3.- SW C port to SW A will be RP
agree
4.- SW B port to SW E will be DP but SW E port to SW B will be blocked
agree
5.- SW E port to SW D port will be RP and DP respectivly
agree
6.- SW D port to SW C port will be RP and DP respectivly
agree

EdTheLad

agustinchernitsky wrote:

Hi all... Just a quick one regarding Root Ports. Imagine this network:


STA would create this topology (correct me here please):

1.- All SW A will be in Designated ports (DP)
2.- SW B port to SW A will be Root Port (RP)
3.- SW C port to SW A will be RP
4.- SW B port to SW E will be DP but SW E port to SW B will be blocked
5.- SW E port to SW D port will be RP and DP respectivly
6.- SW D port to SW C port will be RP and DP respectivly

Is this correct? I think that frames should go from E to D and the C because of the cost of the path (4 + 4 + 19). Is this correct?

Thanks Amigos!

I think you have the right idea but made a mistake when writing No. 4

SW B port to SW E will be blocking but SW E to SW B will be DP.