I have 4 Cisco SG300 series switches running in their DEFAULT configuration. The network was a single /24 subnet. I tried expanding this subnet to a /23.
Original subnet 192.168.30.1 – 192.168.30.254
New subnet 192.168.30.1-192.168.31.254
I don’t think I need to setup VLans in the switches because I don’t have multiple Vlans and would prefer to just keep using the default Vlan.
But I’m having trouble talking between the .31.x devices and the .30.x devices. Traffic is mostly dropped. It will ping once or twice then stop.
When communication goes down if I view the arp -a on a PC that’s having trouble communicating it shows a single Cisco brand MAC for all the devices in the new part of the subnet that it’s unable to ping.
Also I tried swapping these Cisco switches with a single dumb switch and communication worked just fine. I thought the default config for these switches would perform just like a dumb switch (but I guess not).
I’m sure there’s a simple setup on these SG300’s that will allow this but I’m not very familiar with their config utility. I am familiar with Cisco IOS but these gui based devices or very different.
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