Unsolved
This post is more than 5 years old
2 Posts
0
43097
Spanning Tree Port Discarding
Hello,
I have a client with 5 PowerConnect 2800 series switches, one on each floor in a warehouse. This network runs SonicWALL wireless network which has three VLANs:
1 - default
10 - Corporate - has access to domain resources
20 - Guest - no domain resource access, just Internet access
The first floor has a 2848 switch that is the center of the network. The other 4 floors have 2816s.
Each switch has the last 4 ports tagged for VLANs 10 and 20. The 2848 switch has 8 tagged for VLANs 10 and 20. The SonicWALL firewall port dedicated to the WLANs is also plugged into the group of VLAN
Port 14 of each of the 2816s runs to the 48 port switch and is plugged into the ports tagged for VLAN 10 and 20.
Port 1 of each 2816 runs to the untagged ports on the 48 port switch.
Spanning tree protocol is enabled on all switches.
Everything works as expected except the 3rd floor switch. The WLAN cannot connect to the network and wireless clients do not get IP addresses assigned.
I have tracked the issue down to a STP problem where port 14’s state is set to “Discarding”
It appears that the network has a loop and that is why we have this issue.
3rd Floor Switch STP settings
| Port |
STP |
Fast Link |
Port State |
Path Cost |
Priority |
Designated Bridge ID |
Designated Port ID |
VLAN 1 |
VLAN 10 |
VLAN 20 |
| 1 |
Enabled |
Yes |
Forwarding |
4 |
128 |
32768-d0:67:e5:95:d3:e7 |
128-44 |
U |
U |
U |
| 14 |
Enabled |
Yes |
Discarding |
100 |
128 |
32768-d0:67:e5:95:d3:e7 |
128-33 |
U |
T |
T |
| 15 |
Enabled |
Yes |
Forwarding |
100 |
128 |
32768-d0:67:e5:9f:c8:30 |
128-15 |
U |
T |
T |
| 16 |
Enabled |
Yes |
Forwarding |
100 |
128 |
32768-d0:67:e5:9f:c8:30 |
128-16 |
U |
T |
T |
Below is a switch on another floor that works properly
| STP |
Fast Link |
Port State |
Path Cost |
Priority |
Designated Bridge ID |
Designated Port ID |
VLAN 1 |
VLAN 10 |
VLAN 20 |
|
| 1 |
Enabled |
Yes |
Forwarding |
32768-d0:67:e5:95:91:1b |
128-2 |
U |
U |
U |
||
| 14 |
Enabled |
Yes |
Forwarding |
32768-d0:67:e5:95:d3:e7 |
128-43 |
U |
T |
T |
||
| 15 |
Enabled |
Yes |
Forwarding |
32768-d0:67:e5:95:91:1b |
128-15 |
U |
T |
T |
||
| 16 |
Enabled |
Yes |
Forwarding |
32768-d0:67:e5:95:91:1b |
128-16 |
U |
T |
T |
The main difference I see between the two is the Designated Bridge ID. On the working switch, ports 1, 15 and 16 share the same Designated Bridge ID (the MAC address of the switch) while 14 uses the Designated Bridge ID of the 48 port switch.
I have a feeling that the either port 1 or 14 on the 3rd floor switch is plugged into the wrong port on the 48 port switch.
Is there a way to check or match the corresponding switch port through the console? Ie can I do this without going onsite?
Am I doing something incorrectly? Or is there a way to switch the designated bridge ID of the ports on the 3rd floor switch so it does not think this is a loop?
Thank you for your assistance.
Tom
trwitt
2 Posts
0
April 22nd, 2013 11:00
Thank you for the prompt reply. I will try the Lansweeper and update you on the results.
Anonymous
5 Practitioner
5 Practitioner
•
274.2K Posts
0
April 22nd, 2013 11:00
I think looking at what ports the switches are plugging into on the 48 port switch is great place to start. Mapping out port to port plugins can be a bit tricky when not onsite.
In this post another forum user was able to use a 3rd party mapping software to help map out a network and then how to figure out which native MAC corresponds to each port. This was on a 55xx switch, and may be different from the switch you are using, but worth looking at.
en.community.dell.com/.../19500445.aspx
"With LanSweeper I was able to scan my switches and the main MAC address of the switch is assigned to the "internal interface" and the VLANS. Starting from port one the MAC addresses assigned to each port increments up IN HEX from there.
So for instance from my example if my main MAC address for my switch was listed as:
d0:67:e5:yy:xx:19 the ports, starting at port 1, would be d0:67:e5:yy:xx:1a, port 2 d0:67:e5:yy:xx:1b, etc.
So....my interconnected ports are 45 and 47 physical ports up from the first port [59H] therefore: (86 hex - 59 hex= 2d hex = 45 dec) and (88 hex - 59 hex= 2f hex = 47dec) [don't forget this is hex not decimal]"
Keep us updated.