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Quick Stacking Question - PowerConnect 5548
Hello,
I am fairly new to managing switches and entirely new to stacking switches. I recently watched our sys admin setting up new Dell PowerConnect 5548 Switches and was curious about a particular issue with stacking.
We have four switches set up, and they are stacked using the HDMI cables, this is the result from show switch:
DPCStack# show switch
Unit MAC Address Software Master Uplink Downlink Status
---- ----------------- ---------- -------- --------- --------- -------
1 d0:67:e5:7c:fe:54 4.1.0.1 Enabled 2 4 master
2 d0:67:e5:7c:eb:7d 4.1.0.1 Enabled 3 1 backup
3 d0:67:e5:7c:ec:1c 4.1.0.1 Disabled 4 2 slave
4 d0:67:e5:7c:f9:5c 4.1.0.1 Disabled 1 3 slave
Topology is Ring
Stack image auto synchronization is enabled
My question is that the activity light between the links between 1 2 and 3 blinks non stop, but the light on the link between 3 and 4 is almost completely dark. I've only seen it flicker a few times since everything was up and running. What adds to my question is that our file server is on the 4th switch and when moving a large file to or from a host on the 3rd switch, there is no increase on the activity light between the two.
Is there a way to monitor the data usage on the links between switches? Is it normal for one of the links to be lower traffic? I don't have a full understanding of what's going on yet, but our sys admin seemed a bit bothered by it too.
Any input would be appreciated, thanks for your time.
DELL-Willy M
802 Posts
1
June 8th, 2012 10:00
You are going to see a lot more traffic between Unit 1 and 2 as they are the Master and backup members. The Master is managing the whole stack and then relaying all that information to the backup member. The backup member will take over the Master position if for some reason the Master went down.
You can set up Port Mirroring to monitor traffic.
Port Mirroring
Port mirroring monitors network traffic by forwarding copies of incoming and outgoing packets from a monitored port to a monitoring port. Users specify which target port receives copies of all traffic passing through a specified source port.
You can read more about Port Mirroring from the User Guide starting on page 409. Here is a link to the 55xx User Guide.
support.dell.com/.../en_ug.pdf
Hope this helps,
Keep us updated if you can.
ais4ocho
3 Posts
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June 8th, 2012 12:00
That makes sense, but I still don't really understand why the link between 1 and 4 seems to have constant traffic as well, but the link between 3 and 4 is almost dead silent.. Maybe it would help me more to be able to see what it would look like with a 5th switch in the stack and see another link with little activity going through it.
ais4ocho
3 Posts
0
June 8th, 2012 14:00
I should probably just go ahead and clarify that at this point, the activity lights between on either side of 1-2, 2-3, and 1-4 are blinking nearly non-stop, but the activity lights on either side of the 3-4 link are not active at all.
MarcusStarman
2 Posts
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June 15th, 2012 07:00
This document states "In a ring topology all units in the stack are connected to each other, forming a circle. Each unit in the stack accepts data and sends it to the unit to which it is attached. The packet continues through the stack until it reaches its destination. The system discovers the optimal path on which to send traffic."
The stack only uses the 3-4 connection if we disconnect one of the other HDMI cables...but once that cable is reinserted the 3-4 connection shuts off again. Are we just missing a setting somewhere that says "yo, stop pretending you're in a chain topology with failover and use this 4th cable"?
DELL-Willy M
802 Posts
0
June 19th, 2012 10:00
Ring Topology
In a ring topology all units in the stack are connected to each other, forming a circle. Each unit in the stack accepts data and sends it to the unit to which it is attached. The packet continues through the stack until it reaches its destination. The system discovers the optimal path on which to send traffic.
I see a couple different scenarios.
1. if you have the optional cable connected from the 4th switch to the 1st switch then the stack can be using that cable as the optimal patch. As it states in the User Guide.
2. There could be a physical issue with the one of the 3rd of 4th switches. You could move the switches around in the stack order and see if the issue follows the switches around. Physical stacking issues can be hard to diagnose. The switch will work fine as a stand alone and then have issues when stacking. You may need to eliminate one switch at a time for testing to see if a group of switches are responding normally then introduce switches systematically to find the culprit.
Hope this helps,
MarcusStarman
2 Posts
0
June 22nd, 2012 05:00
It appears the stack finds the shortest route from a switch and the master but is incapable of (or not configured for) finding the optimal route between ports. Traffic from g3/0/14 to g4/0/18 will not go directly from g3 to g4 but instead go from g3 to g2 to g1 THEN g4. Can anyone verify?