D-Link Enterprise > DGS-1510-Series

Problem RSTP 2 switches


In my network is 12 switches/
I test RSTP on 2 switches.
1. DGS-1510-52XMP port 25 link to 23 and port 49 link to port 25 (hardware A1, firmware 1.50.B024)
2. DGS-1210-24P (hardware D2 firmware 4.21.B008)

On all switches enable RSTP. Root switch is elected

1. Link one cable on port 25 (1) to 23 (2) ping transmit ok
2. Link one cable on port 49 (1) to 25 (2) ping transmit ok
3. Link two cable on port 25 (1) to 23 (2) and on port 49 (1) to 25 (2)
a. On begin network work ok, computer link on switch 2, server DHCP on switch 1
b. Port 25 (2) is Blocked
c. ipconfig /release
d. ipconfig /renew
e. all led on switch 2 blinking, on switch (1) Utilization  increased from 33% to 43%
f. Transsmision ping drops 10-20% packets afeter 5-10 minutes

what I'm doing wrong?

Upgrade switch 1 to firmware 1.60.012
it's the same

I link my computer to switch 2, run program message analyzer
i see storm packet DHCPACK, DHCPAck, DHCPRequest and DHCPDiscover

I have to set up some special configuration for DHCP ?


I compared what the manuals say about both switches you connected to each other in order to form a loop intentionally.
And I discovered some difference when considering "STP Port Settings":

In both switches you can do STP port settings for groups (ranges) of ports, but when you do so, switch DGS1210-24P (in contrast to DGS-1510-52) forms a separate Spanning Tree per port group, while switch DGS-1510-52 seems to operate only a single Spanning Tree instance regardless of how many port groups might be configured for this switch.

Hence, if ports 23 and 25 at switch DGS1210-24 happen to belong to different port groups/ranges, a loop might be the result for VLANs defined for both ports (access or trunk).

So, to prevent this, at switch DGS1210-24P you must ascertain that all ports that are connected to other switches (or just all ports 1-24 of the switch) belong to the same  STP port group/range.

Just an idea only, may be I'm completely wrong ...



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