Bad Subnet Configuration on my Cisco 3750?
Posted on 2007-10-15
I have a 24-port Cisco 3750 switch that has been configured by a 3rd-party consultant who is no longer available to me, so I need help understanding and correcting this problem...
First, I will describe the current configuration to the best of my ability: The switch is configured with one VLAN (the default). The switch is on IP address 192.168.0.1, and it is configured as the default gateway for the 192.168.0.0 subnet (let's call it "Subnet A") on my in-house network. Port 3 on the switch is configured as the router for "Subnet B" (192.168.10.0), also in-house. Clients in Subnet B (10.0) are configured to use 192.168.10.1 (port 3) as their default gateway. The only reason we created Subnet B was to add available IP addresses; at the time, we did not have a need to isolate traffic between the subnets.
The PROBLEM is that all Subnet B clients are required to uplink to the 3750 switch via Port 3. For some reason, I cannot connect Subnet B clients to any other port on the switch and have communication with Subnet A. Is this supposed to be the case? What can I do to allow the two subnets to communicate with each other from any port on the switch?
It seems to me that the consultant should have created VLANS instead of setting one port to be a router for one of the subnets, but this is NOT my area of expertise.
I am fast approaching the need to isolate traffic from other subnets, so this problem is critical to me. Thanks for any help you can provide!