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encounter every XX seconds network topology change

On our network we encounter every XX seconds network topology changes

 

This is alwasy on the SG220 Types

The Catalyst 2960x

 

On the SG220 devices we don't see these changes

 

Everything is in RSTP

All they switches are on the latest firmware except the Catalyst.

 

What could be the reason

14 Replies 14

Hello,

 

post a schematic drawing of your topology. Is there anything showing in the logs ?

hello

 

i post here a schematic ( no visio :-( still waiting for license)

Each blue block = a Switch

Yellow Star = encounter network topology change

White block = No cisco switch

 

 

i'm brand new to Cisco , so don't know how to look at the logs

 

 

Joseph W. Doherty
Hall of Fame
Hall of Fame
Are edge ports configured with PortFast?

it guess there are too many hops between two "leaves" of this tree for spanning-tree to converge

this is why a star topology or access - ( distribution- ) core topology are common.

conversion to MST may also help because number of hops are less important

 

do you have idea what switch is the root of your tree?

It can help to manually configure the root of the spanning-tree to a central point in your network by configuring the spanning-tree priority

 

STEPAN JANKOVIC
Level 1
Level 1

Hello,

you have to track down, where are these changes happening. As was already written, your edge ports have to be portfast ports, to not generate TCN. It is true that your network STP diameter is high and topology should be simplified. STP Root has to be located in the core and fixed by manual configuration. I believe, that during implementation of these steps, you will evade the issue.

Regards

Stepan

The bad network topology is something from the past , ATM we are design a new network topology

 

In the meantime we have to solve this problem , because every xx second there is also a outage of the network , so i suppose the reason is also the topology change.

 

In the past all the switches are put directly in the network without any setting , so every priority is on the default , so the Root Bridge  is the switch with ip : 10.0.0.60

 

Today i will look to put every edge port in his correct setting and analyse.

 

i'm a little afraid if i change the priority , the network will be unreachable or can i do it without any problem and put the priority of the 10.0.0.152 in the lowest ?? 

Hello,

 

judging from your topology drawing, you have one 2960X switch, and the rest are SG200 switches ? How many VLANs do you have ? Since your topology is constantly changing, you need a solution. I would set the 2960X as the root for all your VLANs.

 

Before changing anything, post the output of:

 

show spanning-tree vlan x (where 'x' is the Vlan, if you have more than 1 Vlan, run the command for each)

show spanning-tree root

hello

 

thank you 

 

Above my catalyst there is also a Allied telesis

 

Also i have SG220 switches where i see the topology changes , on the SG200 they are stable

 

the command you asked

 

SWSERVER#show spanning-tree vlan 1

VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 32768
Address 0057.d2ea.4913
Cost 40000
Port 3 (GigabitEthernet1/0/3)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address f078.167a.f200
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec

Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/0/1 Desg FWD 20000 128.1 P2p
Gi1/0/2 Desg FWD 20000 128.2 P2p
Gi1/0/3 Root FWD 20000 128.3 P2p
Gi1/0/4 Desg FWD 20000 128.4 P2p
Gi1/0/6 Desg FWD 20000 128.6 P2p
Gi1/0/11 Desg FWD 20000 128.11 P2p
Gi1/0/12 Desg FWD 20000 128.12 P2p
Gi1/0/15 Desg FWD 20000 128.15 P2p
Gi1/0/16 Desg FWD 200000 128.16 P2p
Gi1/0/18 Desg FWD 20000 128.18 P2p
Gi1/0/21 Desg FWD 20000 128.21 P2p

 

SWSERVER#show spanning-tree root

Root Hello Max Fwd
Vlan Root ID Cost Time Age Dly Root Port
---------------- -------------------- --------- ----- --- --- ------------
VLAN0001 32768 0057.d2ea.4913 40000 2 20 15 Gi1/0/3
VLAN0100 32868 f078.167a.f200 0 2 20 15

 

 

Hello,

 

what is connected to interface GigabitEthernet1/0/3 ? Is that the Allied Telesys ?

 

Either way, you appear to have only 1 Vlan. Check first if the Allied Telesys is connected to that port. If not, and if the port goes to an SG2xx switch, make the 2960 the root for your network:

 

2960(config)#spanning-tree vlan 1 root primary

 

Since the network may converge, some downtime (we are talking seconds) is possible, so you might want to do this after hours...

hello

 

Port 1 goes to te Allied Tellesis ( 10.0.0.152)

 

Port 3 goes to 10.0.0.51

 

At the moment i started to set every port who is not connected or connected to a Client to Edge  = enabled

Hello,

 

so interface GigabitEthernet1/0/3 goes to one of the SG switches ? Then that is probably where your troubles start. Try and set the 2960X as the root (as described in an earlier post)...

hello 

 

At the moment i changed port to Fast where possible

 

Now everything is stable for more then 2 hours

 

I will try the  command to put the catalyst into Root , now mardi , then there is a server restart so i can have a little downtime.

 

Hope this will be the solution

Actually, if your network remains stable with the changes you have made, hold off on setting the root Vlan. I would only do that if the network shows unstability again...

I agree with Georg Pauwen especially because you all ready picked up the redesign of the network

- if your network is stable at this time ->  no immediate changes necessary

- if STP topology change reoccurs ->  first change the spanning-tree priority so the 2960 is the root
   the impact (if any) will be similar to a topology change, but now only once (no other outage expected).

- proceed with the redesign of the network topology to a more common setup as soon as possible.

- with above in mind when it is necessary to expand your current network (add more switches) ,
   changing the STP root may be a first thing to do

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