[chbot] DHCP questions

[Henri Shustak]

Hello, 

I suspect that your wireless access points are **not** acting as a bridge and instead are each running their own DHCP server is that possible?

Henri 

> On 17/08/2022, at 2:32 PM, Robin Gilks <gb7ipd at gmail.com> wrote:
> 
> Hi Volker
> 
> I'm up to speed on basic DHCP, I've been running my own server for over 20 years including PXE booting of dumb clients, fixed MAC address mapping, blacklist and white list configurations.
> 
> What I don't get is how to prevent a client that roams from one AP to another from losing its DHCP allocated address due to either not refreshing or starting from scratch on each roam.
> 
> I feel it's something to do with VLANs and managed switches but I just don't know enough of the vocabulary to hold a conversation
> 
> 
> On Tue, Aug 16, 2022 at 5:28 PM Volker Kuhlmann <list57 at top.geek.nz> wrote:
> Hi Robin,
> 
> > Didn't have time last night to follow all the information about DHCP and
> > network spanning etc. The conversation was getting outside my current
> > knowledge base so if someone can point me at a couple of relevant articles,
> > so I can digest the basics and can then have a meaningful chat with our
> > networking suppliers on how their product works, that would be great.
> 
> Generic beginner rundowns on DHCP should be on the net, but I don't know
> any off-hand. Ignore DHCP6 (DHCP for IPv6).
> 
> The basics are simple enough though. DHCP is a protocol which endpoints
> can use to obtain an IP address. It uses broadcasts, for obvious
> reasons. The DHCP server grants a lease of an IP address which is valid
> for a certain time, after which the client must request a new one.
> Servers can be configured to allocate a static IP based on the MAC
> address of the client.
> 
> Things like your ATA basically always default to DHCP - least messing
> around for the manufacturer. If they default to a fixed IP it's probably
> printed on the label. The box's web interface may allow to configure
> anything, factory reset should undo all that.
> 
> It's easiest to start with DHCP. You can check with nmap -sP .../24
> where the thing might be address-wise.
> 
> There's a problem when the box's IP address is not on your computer's
> network (with DHCP that doesn't happen). In that case alias another IP
> address to your network interface (ip command, ifconf has been
> deprecated for many years and may not be installed by default). Then run
> nmap. You can alias a /16 if you need to. Pick any number for your own
> interface but not the one the box has. 33..219 should be OK. Cake if
> you collide...
> 
> This holds for any network box, but things get a tad more complicated if
> there is more than one RJ45 shaped hole in it.
> 
> HTH
> 
> Volker
> 
> -- 
> Volker Kuhlmann
> http://volker.top.geek.nz/      Please do not CC list postings to me.
> 
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