Network Crashes after intro of new switches

[baracas77]

Hi,

I've recently purchased 2 SG-300s (28 & 52 port) to add to our network.  the network consists of other switches ie SRW2048/2024 and a couple of 3coms which are being replaced.  There's no vlans set up and the switches are pretty much running vanilla except with a static ip assigned.

I've been in to the admin interface to set an ip which I know is free and then when I plug either of these new one's into our main switch, the whole network dies.  Nothing at all pings.  Unplug them and it's all good again.

Configuring switches is not one of my strong points so apologies if i'm missing anything blindingly obvious, but any help would be greatly appreciated.

Cheers

[Steven36810]

Hello Matt ,

Please tell me more about your network , you can be connected but not have a route or path from on point to the other. If there's a cable or speed mismatch you won't have connectivity and the ports need to have same configuration as well as being static instead of switchport. help this helps and please feel free to ask as many questions.

Sent from Cisco Technical Support iPhone App

[fgasimzade]

Make sure there is no loop with your new switches added to the network

[garapoglou · Accepted solution]

Hi,

I suspect there's a loop somewhere. Have you checked the connections when you added the new switches? Is STP enabled on your network?

Best regards,

Giorgos

[baracas77]

Yep, nailed it.  STP was the issue.  Many thanks guys.

[baracas77]

Hi guys, thanks for all your replies.  Having checked out the current switches where STP is disabled, it's looks like the new are enabled by default.  Question is, should I enable on the old ones or disable the new ones?

[Peter Paluch]

Hello,

Regarding the STP, you should run it for all VLANs on all your switches. Each switch should run the same version of STP for all VLANs.

Best regards,

Peter

[baracas77]

We don't actually have any vlans.  Therefore, is STP necessary?

[jimmysands73_2]

You always have the default VLAN.

[garapoglou]

Hi,

Glad you solved it.

STP has to be enabled to avoid loops, no matter whether there are many VLANs or the default one. STP is one of the most important protocols concerning switching.

Best regards and thanks for rating.

Giorgos