Maybe I'm pulling at a fake distinction here but the progenitor blog posts of this format that I'm thinking of were incorrect models of constructs that almost everyone uses in their everyday life constantly ( names, dates, time etc )
Whereas I find it kinda unlikely that someone both knows what a DHCP server is, and holds a belief that there is only ever exactly one on their network?
In theory it's fine to have multiple DHCP servers as long as they don't step on each other. But in reality a bunch of the things mentioned in this post are ways for the network to be hosed. Unfortunately, enough LANs are semi-hosed that it's worth working around known problems.
At work I manage a network with two DHCP servers. One is a dnsmasq that assigns the IP address, hostname, and basic network parameters to all network devices, and the other is a LTSP server (https://ltsp.org/) that provides network boot images only for certain devices that require it. It might not look pretty, but it works really well.
What really matters is that there's a coherent policy for assigning addresses, which is absolutely compatible with having multiple DHCP servers on the same subnet (e.g. each server configured to hand out non-overlapping IP ranges).
You don’t have to have one. My first LAN didn’t. I had no idea what I was doing and picked 17.0.0.0 addresses for local ones and I couldn’t connect to Apples website.
I've never heard of a LAN without IP addresses. Is that a thing? I'd assume that no IP addresses means you can't even use TCP/IP at all, right? Is there something else you'd use instead?
I get the idea, but this isn't necessarily useful as advice and toys with definitions. It's ESPN levels of conversation-baiting. Lots of assumptions can be reasonably made about residential LANs without being true of enterprise LANs/DMZs.
If a residential LAN is RFC1918 and has no NAT, then it is still a LAN... without internet access.
Then the "A & !A" fallacy of "MAC addresses can’t be changed. MAC addresses can be changed."
Just kind of a mess. Would be more interesting to explore the edge cases rather than throw out half-truths and 0.05% instances.
Port- or Client-isolation on Ethernet switches and Wi-Fi access points respectively. Often seen in corporate environments and (properly configured) guest networks.
There are recent "client isolation" features that prevent P2P communication. Some hosting providers also block customers on the same LAN from attacking each other.
Did arp poisoning in school and used a tool to show images from websites people visited on the projector. Teacher thought it was fun until someone went to goatse.
Switches and firewalls can do all kinds of things. Probably the most common case is that public/guest wifi networks often have client isolation set up so that different devices on the network can't contact each other. Same subnet, but only access to the gateway and the internet in practice.
(Also can happen if ARP is not working correctly, which can be a right PITA to debug).
Most consumer wifi routers I’ve used have a setting to prevent peer-to-peer traffic. Whether this still counts as being on the same subnet is kind of a philosophical question.
Whereas I find it kinda unlikely that someone both knows what a DHCP server is, and holds a belief that there is only ever exactly one on their network?
* two people who say they are on the same LAN agree on what the LAN is
Programmers think the models they use are perfect.
There'd better be or your network is probably hosed.
I've never heard of a LAN without IP addresses. Is that a thing? I'd assume that no IP addresses means you can't even use TCP/IP at all, right? Is there something else you'd use instead?
If a residential LAN is RFC1918 and has no NAT, then it is still a LAN... without internet access.
Then the "A & !A" fallacy of "MAC addresses can’t be changed. MAC addresses can be changed."
Just kind of a mess. Would be more interesting to explore the edge cases rather than throw out half-truths and 0.05% instances.
I like the GNOME 2006 era though.
Barring "very buggy software," when is this false?
This isn't even that recent. I remember doing ARP poisoning exactly once and then being surprised that it didn't work everywhere.
I think the falsehood here is that same IPv4 subnet = same link layer network, but that doesn't have to be the case.
This isn't even that recent. I remember doing ARP poisoning exactly once and then being surprised that it didn't work everywhere.
(Also can happen if ARP is not working correctly, which can be a right PITA to debug).
Edit: fair point. Maybe not.
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