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PC7048 and N1524 spanning tree issues

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PC7048 and N1524 spanning tree issues

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hi all,

I'm trying to do the following :

PC7048 TRUNK VLAN 300 Gi1/0/38 <--> N1524 (access mode vlan 300) Gi1/0/21

It seems this cause an issue, as DISCARDING port state is shown below:

PC7048#show spanning-tree blockedports

Spanning tree Enabled (BPDU flooding : Disabled) mode rstp
CST Regional Root: 80:00:F8:B1:56:2E:75:C2
Regional Root Path Cost: 0


###### MST 0 Vlan Mapped: 1-2, 240, 300, 500
ROOT ID
Priority 32768
Address D067.E599.4FA0
Path Cost 62000
Root Port Gi1/0/44
Hello Time 2 Sec Max Age 20 sec Forward Delay 15 sec
Bridge ID
Priority 32768
Address F8B1.562E.75C2
Hello Time 2 Sec Max Age 20 sec Forward Delay 15 sec
Interfaces

Name State Prio.Nbr Cost Sts Role RestrictedPort
------ -------- --------- --------- ---- ----- --------------
Gi1/0/38 Enabled 128.38 20000 DSC Altn No

The config is the following on PC7048:

interface Gi1/0/38
description "ToDellN1524WAN-Gi1/0/21"
switchport mode trunk
switchport trunk allowed vlan 300
exit

Interface details:

PC7048#show interfaces detail Gi1/0/38

Port Name Duplex Speed Neg MTU Admin Link
State State
--------- --------------------------- ------ ------- ---- ----- ----- -----
Gi1/0/38 ToDellN1524WAN-Gi1/0/21 Full 1000 Auto 1518 Up Up

Port Description
-------- ----------------------------------------------------------------------
Gi1/0/38 ToDellN1524WAN-Gi1/0/21

Flow Control:Enabled
Port: Gi1/0/38
VLAN Membership mode:Trunk Mode

Operating parameters:
PVID: 1
Ingress Filtering: Enabled
Acceptable Frame Type: Admit All
Default Priority: 0
GVRP status:Disabled
Protected:Disabled

Port Gi1/0/38 is member in:


VLAN Name Egress rule Type
---- --------------------------------- ----------- --------
300 MNGT Tagged Static

Static configuration:
PVID: 1
Ingress Filtering: Enabled
Acceptable Frame Type: Admit All

Port Gi1/0/38 is statically configured to:

VLAN Name Egress rule
---- --------------------------------- -----------
300 MNGT Tagged

Forbidden VLANS:
VLAN Name
---- ---------------------------------
1 default
2 VLAN0002
240 Interconnect
500 vMotion


Port Gi1/0/38 Enabled
State: Discarding Role: Alternate
Port id: 128.38 Port Cost: 20000
Port Fast: No (Configured: no ) Root Protection: No
Designated bridge Priority: 32768 Address: F48E.3815.E077
Designated port id: 128.21 Designated path cost: 62000
CST Regional Root: 80:00:F4:8E:38:15:E0:77 CST Port Cost: 0
BPDU: sent 1854, received 3783

On the N1524:

vlan 300

name MNGT

interface Gi1/0/21
description "MNGTtoPC7048-Gi1/0/38"
exit

So, as you can see , nothing is on the N1524....but, the PC7048 is blocking the port...even if i chhange the interface,... i don't understand why.

Many thanks at all for your help !

All Replies
  • i tried configure the interface as below on the N1524:

    interface Gi1/0/21
    description "MNGTtoPC7048-Gi1/0/38"
    spanning-tree portfast
    switchport access vlan 300
    exit
    !

    But port on PC7048 still blocking ...

    Name State Prio.Nbr Cost Sts Role RestrictedPort
    ------ -------- --------- --------- ---- ----- --------------
    Gi1/0/38 Enabled 128.38 20000 DSC Altn No

    The final aim is to be able to connect the N1524 by using SSH...so L3 with ip address..

    Driving me crazy !

  • A couple of things to look at.

    The switchport mode should be the same on both switches. Trunk mode is sending and receiving tagged packets, while access is sending and receiving untagged. 

    Spanning tree comes into play when there is a physical loop in the network. I would double check your physical connections for multiple cables connecting from switch to switch.

    Let us know what you find.

    Daniel Covey
    Dell EMC | Enterprise Support Services
    Get support on Twitter: @DellCaresPRO

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  • Hi,

    Thanks for your reply, topic is solved, i made a loop... that's why the port was blocking.