3 Cisco WS-C2960S-24PS-L floods network

[dknudson007]

I have three new 2960 switches as listed in the title. I configured them as follows:

192.168.1.215     host: whse-c

192.168.1.216     host: whse-b

192.168.1.217     host: whse-a

Switches B and C flow into A before continuing on into the server room switch (distance issues).

All three switches are configured for ports 21-24 at 1000 and set as cisco switches. all other ports are undefined as they have a myriad of desktops, printers and non cisco access points flowing into them. side question - should i configure them as access points where applicable even if they are non cisco??

I am replacing three netgear switches that currently are in place and have no known issues other than they are old and the fans may fail soon.

I had the following problems:

hooked up .217. was able to get to it from the network. Hooked up 215 and then 216.  All the sudden I lost the ability to tap into the switches, any of them. (I think I had done 215 at that point too, before adding 216.  I found out later it took the network to its knees as internet was lost, and the MPLS stopped functioning.

I undid the changes and put the netgears back in service and all was right with the world again.  At first I thought it was a bad host name as I had used whse-a on switch C in error. I changed that after this issue.

Later that day I put 215 in place. checked it from the network and could get to it just fine. Then I put 216 in service. I lost connection to 215. I could no longer get to the internet from my pc and the MPLS went down again.  This time I just unhooked 216. 215 is still in place and working on the network at the moment and not causing issues. (btw these switches are not even in my path from my pc to the internet, just on the same network)

tomorrow I am going to try 217 again while 215 is still on the network and see if there are any issues adding that swtich. if I can do so, and there are no problems, is this an indication of a faulty switch?  what further testing can I do, have I missed something in setup?  If this brings the network down again, why cant i add two of these switches to each other/on the same network path (B and C were not even connected to each other yesterday evening when it went down again).

thanks

dave

[Joe Lentine · Accepted solution]

Hello
I would need a little more background info on your network to troubleshoot your apparent loop or broadcast storm. Ex. Where is router, any vlans, ect....

So here is for starters.

- host name will not affect the operation. It would only affect telnet or ping if yours using Dns lookup to ping or telnet to your switches.

- configure all ports besides your uplinks as access ports and use spanning tree portfast. Ex-
#interface range gig 1/0/1-20
#switchport mode Access
#switchport access vlan xxx
#spanning-tree portfast

- then take your uplink ports and configure them as trunks. Then configure uplink fast

#switchport mode trunk
#spanning-tree uplink-fast


I would recommend running c into b and then b into a. This will help prevent any loop and decrease latency.

Make sure you have default gateways on all switches so they know where to send traffic.



Sent from Cisco Technical Support iPhone App

[dknudson007]

Thanks for your above explanation.

Because of physical location, sending C into B then into A is not possible.They are in three different locations with A being the the last in line before the server room switch.  Multiple switches were necessary due to the 300' 5e limitation in getting back to the server room.

To this point I have only looked at the Gui ADSM when working with these switches. I am assuming that the code you have above is what needs to be added via CLI, Enable/config t?

There are no vlans except what is set by default.

Router C in in one area of the Warehouse.

Router B is in another area of the warehouse

Router A is the router closest to the server room and services the warehouse as a whole.

I only want ports 21-24 at gig. Those were going to be the "trunks" as you define them?

in further testing I found out the following:

I left Router C as configured. I placed router A into service and the network failed again. I unplugged C from A in port 21 and put it in port 15. 15 was an unconfigured port. Network went stable. I then changed 21-24 back to unconfigured (none) and replugged 15 into 21 (back to gigabyte speed). network remained stable. I then configured router B as I had A and turned it on. Network is stable.

I dont know what is wrong in the programing of using "Cisco Switch"  in the smartport section of the GUI, but doing do makes it major fail even if two stiches are not plugged together (if B and C were active but plugged into the old switch at A, the firestorm still happened).

the options are Switch, router, phone +desktop, access point and none.

you mentioned configuring as Access ports....is that the same in the gui as Access point?

At the moment, I am not configured for optimal use of the switches, but they are in place and working. However, I would like to take advantage of their capabilities.

Can you either give me instructions related to the gui, or give the actual commands if CLI?

if you need more info, please let me know. BTW, I do have a gateway entered in.

I can provide screen shots etc if need be of the configuration in Gui if this will take them?

thanks in advance