1 WAN and 2 LAN - Into one switch?
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I'm starting to wonder if that single switch can handle two different subnets going throug hit.
Is that possible?
Its not a layer-3 but I can't imagine us doing it this way unless it was possible.
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It is possible, but it will lead to problems. Far better to buy a second switch and keep them separate.
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If the switch supports VLANS you can do this, otherwise you'll need two switches.
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Its just a basic switch. No vLANs supported. Does that mean I need two switches for each subnet?
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You need one per subnet.
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Multiple subnets on a single switch is rarely a problem (even in a single VLAN)… we've been doing that for years on a myriad of different switches.
I suspect the issue is likely to be in the NAT config in this case. -
You really don't want to mix subnets on a single switch. It's possible, may require a little manual oubound NAT configuration in this case, but it's MUCH better to just run one subnet per interface.
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Sharing a switch messes up clients that attempt to get address using DHCP if there are DHCP servers on each subnet. There also can't be any control over which network someone decides to put their computer in rendering strict firewall rules on one interface pointless because a client can change their address to the other network.
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If your switch supports "port based" VLANs (as distinct from "TAG" based VLANs) you could set up two distinct LANs: one for your "red" clients, one for the "green" clients. That should keep the DHCP broadcast traffic separate.
But basic switches are "small change" nowadays.
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Sharing a switch messes up clients that attempt to get address using DHCP if there are DHCP servers on each subnet. There also can't be any control over which network someone decides to put their computer in rendering strict firewall rules on one interface pointless because a client can change their address to the other network.
Sure, but if you don't use DHCP then it isn't an issue. I was mainly pointing out that running more than one subnet on a single VLAN technically isn't an issue. Running it behind pfSense using NAT, DHCP etc is where there are issues. It is of course difficult to put more than one IP on an interface with pfSense but we've had FreeBSD firewalls running IPFW with up to six different IP ranges behind them, so technically I can swear that it works if you use firewalls and firewalling methods that support it.
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I agree that it works. I'm just pointing out that you lose the security gained from separate subnets because clients can easily roam between them. We do it for certain pieces of the campus; however, when you do it correctly with VLANs, it creates more security and network segmentation possibilities for hosts based on their purpose.
If a VLAN capable switch isn't available, just be aware of the security concerns and aggregation of the broadcast domains.
