ASDL Modem with Different Subnet To internal LAN
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This is a very basic question, and not specifically related to pfsense. I just need someone to kindly briefly explain it.
Many ADSL broadband connections are setup by using ADSL modem with (for example) an IP of 192.168.1.1, connected to a WAN port on a router/firewall with 192.168.1.2 for the WAN, and internal LAN IP of 192.168.0.1 where the main internal network resides. This all works, and I just accept it. I guess it's the NAT on the router which is bridging the two different subnets.
What I'd like to know, is why the ADSL modem is often on a different subnet to the router?
Are there security advantages to setting it up this way?I know I can change the IP of the modem to 192.168.0.2 if I wanted and it will still work. So I guess I'd just like this gap in my knowledge filled.
Many thanks.
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I'd suggest you read about subnets. Each network must have a different subnet, which is why one has 192.168.0.x and the other has 192.168.1.x.
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Thanks Cry Havok,
Following your advice; I have read the wikipedia page, and gone on to watch numerous you-tube videos on IP addressing, subnets, subnetting and vlans. I have learned a great deal, and what I take from it to answer my own question is it just seems to be mainly about minimising the broadcast of network traffic to hosts which don't need it. I also realise there are security benefits with vlans where a separate network is created, and not joined unless a layer 3 device is used.
Therefore the way I see it , there is no reason to set the ADSL modem to be on the same subnet as the internal LAN. Just one less device to receive broadcasts on the internal LAN!
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Not only is there no point, but you'll probably find your network stops working unless you bridge the WAN and LAN interfaces on the pfSense host.
