I originally had several items on my LAN, with fixed IP's configured
within the devices themselves, such as an IP cam, routers and printers.
Everything else relied on the router's DHCP to allocate an IP, when
they connected.

As time as passed and my LAN has become busy with things connected,
some things have been unable (despite there being unused addresses), to
be allocated an address without a reboot (laptops). I recently added 8x
Smart Plugs, which exacerbated the problem, so I thought to try setting
up almost everything without a fixed IP, a router allocated IP's.

My main router, which connects to FTTC is runs OpenWRT, which does not
allow a reserved section of IP's for static addresses. Rather it seems
to use a sort of intelligent reserve, where it DHCP allocates above the
static IP's.

Coming to the question now....
I have now set every item which connects to my LAN, either with an IP
in the device, or a static address in my router. No more issues with
laptops failing to acquire an IP after waking. One thing I have also
noticed, is that my IP cam's frame rate has rocketed. It is specified
as 25fps, prior to the above changes it would manage around 2 to 5 fps.
It now manages 10 to 18fps depending on the picture content.

The IP cam connects to my main OpenWRT router, that is wire connected
to a second router, the second router connects via wifi to my laptop,
which is what I am viewing the IP cam on. Why should the fps suddenly
improve?

Harry Bloomfield wrote:

My main router, which connects to FTTC is runs OpenWRT, which does not
allow a reserved section of IP's for static addresses.

You can set a pool of DHCP addresses, whatever is outside the pool is
available for static assignment

https://openwrt.org/docs/guide-user/base-system/dhcp#dhcp_pools

Harry Bloomfield wrote:

Why should the fps suddenly improve?

Might you have previously had a clash of IP addresses?

On 26/09/2020 12:14, Harry Bloomfield wrote:

I originally had several items on my LAN, with fixed IP's configured
within the devices themselves, such as an IP cam, routers and printers.
Everything else relied on the router's DHCP to allocate an IP, when they
connected.

As time as passed and my LAN has become busy with things connected, some
things have been unable (despite there being unused addresses), to be
allocated an address without a reboot (laptops). I recently added 8x

It might be that the router has them allocated to other MAC addresses
and the lease has not yet expired.

On networks with lots of devices connecting and disconnecting it can
make sense to lower the DHCP lease time to allow addresses allocated to
now dormant devices to be re-used sooner.

Smart Plugs, which exacerbated the problem, so I thought to try setting
up almost everything without a fixed IP, a router allocated IP's.

My main router, which connects to FTTC is runs OpenWRT, which does not
allow a reserved section of IP's for static addresses. Rather it seems
to use a sort of intelligent reserve, where it DHCP allocates above the
static IP's.

Have you made sure that you have no fixed IPs set in your DHCP pool?

Typically you want the router to say start allocating DHCP addresses
from 192.168.x.100, with a pool of say 100 addresses, then make sure
that all static devices are in the 192.168.x.2 - 192.168.x.99 or
192.168.x.201 - 192.168.x.254 range.

Coming to the question now....
I have now set every item which connects to my LAN, either with an IP in
the device, or a static address in my router. No more issues with
laptops failing to acquire an IP after waking. One thing I have also
noticed, is that my IP cam's frame rate has rocketed. It is specified as
25fps, prior to the above changes it would manage around 2 to 5 fps. It
now manages 10 to 18fps depending on the picture content.

The IP cam connects to my main OpenWRT router, that is wire connected to
a second router, the second router connects via wifi to my laptop, which
is what I am viewing the IP cam on. Why should the fps suddenly improve?

It sounds like you had an IP address conflict before.

Sometimes having a quick peak at the PCs ARP table can tell you
interesting stuff:

arp -a

You can then lookup the cached mac addresses[1] and see whether they
actually correspond to the manufacturer of the device you were expecting
(and also whether they stay consistent or flip between macs).

[1] Various web sites like:

http://www.coffer.com/mac_find/
https://macvendors.com/


For example, taking a snippet from the results on one of my machines I get:

C:\Users\Johnarp -a

Interface: 192.168.1.13 --- 0x3
Internet Address Physical Address Type
192.168.1.1 00-1d-aa-71-71-48 dynamic
192.168.1.2 00-50-7f-f1-1a-32 dynamic
192.168.1.4 f4-ec-38-aa-28-a8 dynamic
192.168.1.10 24-5e-be-04-e4-18 dynamic
192.168.1.11 00-18-dd-23-22-3c dynamic
192.168.1.12 38-2c-4a-bc-58-e3 dynamic

(note that the "dynamic" reported here is just indicating that the
address has not been specified as static on the PC itself - its not a
reflection of if they are actually dynamic addresses on the network)

Which if you look em up shows, Draytek, Draytek, TP-Link, QNAP, Silicon
Dust Engineering, ASUSTek Computer Inc

Also has your second router got its DHCP server enabled? You only want
one DHCP server active per subnet, or otherwise there is a danger of
address conflicts unless you have carefully set them up to allocate
addresses from non overlapping pools, and also outside the range used
for any static IPs.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:

You only want one DHCP server active per subnet

Generally, yes you do

or otherwise there is a danger of address conflicts

Though openWRT can cope with multiple non-authoritative DHCP servers,
I've not checked what it does, but probably gratuitous arp on behalf of
the address it proposes to lease?

Andy Burns wrote on 26/09/2020 :
You can set a pool of DHCP addresses, whatever is outside the pool is
available for static assignment

https://openwrt.org/docs/guide-user/base-system/dhcp#dhcp_pools

Thanks, I might give that a go. I hadn't spotted anything in the set up
menus..

Andy Burns presented the following explanation :
Might you have previously had a clash of IP addresses?

I don't think so, it always ran at the earlier speed, even before I
swapped out the router for the OpenWRT one. Before it had a static IP,
but in a reserved area of IP's.

John Rumm laid this down on his screen :
On networks with lots of devices connecting and disconnecting it can make
sense to lower the DHCP lease time to allow addresses allocated to now
dormant devices to be re-used sooner.

That makes sense, I did always wonder why the lease time was
adjustable.

Andy Burns was thinking very hard :
Though openWRT can cope with multiple non-authoritative DHCP servers, I've
not checked what it does, but probably gratuitous arp on behalf of the
address it proposes to lease?

It's a while since I last messed around with my routers and stupidly,
at first I tried setting the static addresses on my none OpenWRT
router, which is not the DHCP server, yet serve most of the IP's. I was
then puzzled as to why the IP's of the items on my LAN remained as
before, until it dawned on me.

Harry Bloomfield wrote:

Andy Burns wrote on 26/09/2020 :
https://openwrt.org/docs/guide-user/base-system/dhcp#dhcp_pools

Thanks, I might give that a go. I hadn't spotted anything in the set up
menus..

It's odd that LUCI doesn't expose it (unless there's an add-on module?)
you can do it from ssh

On 26/09/2020 14:18, Harry Bloomfield wrote:
John Rumm laid this down on his screen :
On networks with lots of devices connecting and disconnecting it can
make sense to lower the DHCP lease time to allow addresses allocated
to now dormant devices to be re-used sooner.

That makes sense, I did always wonder why the lease time was adjustable.

Worth noting that with much modern kit it may preserve a cache of MAC /
IP pairs even after lease expiry, so it can re-issue the same address
later where possible (although it can still re-allocate and address if
the lease has expired and it has run out of free pool addresses to meet
the current demand)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:
On 26/09/2020 14:18, Harry Bloomfield wrote:
John Rumm laid this down on his screen :
On networks with lots of devices connecting and disconnecting it can
make sense to lower the DHCP lease time to allow addresses allocated
to now dormant devices to be re-used sooner.

That makes sense, I did always wonder why the lease time was adjustable.

Worth noting that with much modern kit it may preserve a cache of MAC /
IP pairs even after lease expiry, so it can re-issue the same address
later where possible (although it can still re-allocate and address if
the lease has expired and it has run out of free pool addresses to meet
the current demand)

Always true in my experience with routers over the past several years,
the router always assigns the same IP to a given MAC address unless you
explicitly tell it not to.

--
Chris Green
·

Chris Green has brought this to us :
Always true in my experience with routers over the past several years,
the router always assigns the same IP to a given MAC address unless you
explicitly tell it not to.


The problem I was seeing, was with (both his and hers) laptops coming
out of hibernation, having no connection to a router and sometimes not
even showing my routers in the wifi list. It would show lots of other
local ones, just not mine, or if it did would report as being unable to
connect to them.

The only way to regain a connection, was to run a cold-boot.

In article ,
Chris Green wrote:
Worth noting that with much modern kit it may preserve a cache of MAC /
IP pairs even after lease expiry, so it can re-issue the same address
later where possible (although it can still re-allocate and address if
the lease has expired and it has run out of free pool addresses to meet
the current demand)

Always true in my experience with routers over the past several years,
the router always assigns the same IP to a given MAC address unless you
explicitly tell it not to.

Yes. I have a fairly old BT router. Ages ago, I did a list of what was
where - as this ancient machine prefers a fixed IP address. Did the same
recently - and was surprised to see the various Wi-Fi devices that aren't
on all the time still had the same ones.

It also has the ability to lock a MAC address to an IP one too.

--
*Tell me to 'stuff it' - I'm a taxidermist.

Dave Plowman London SW
To e-mail, change noise into sound.

On 26/09/2020 16:22, Harry Bloomfield wrote:
Chris Green has brought this to us :
Always true in my experience with routers over the past several years,
the router always assigns the same IP to a given MAC address unless you
explicitly tell it not to.


The problem I was seeing, was with (both his and hers) laptops coming
out of hibernation, having no connection to a router and sometimes not
even showing my routers in the wifi list. It would show lots of other
local ones, just not mine, or if it did would report as being unable to
connect to them.

That I have found that is quite often a laptop problem where if you
sleep and wake it enough times, then the wifi just stops behaving in any
sensible way. Sometimes only a power off and back on again (i.e. not
just a restart) will fix it.

The only way to regain a connection, was to run a cold-boot.




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sat, 26 Sep 2020 14:18:14 +0100, Harry Bloomfield, Esq. wrote:

John Rumm laid this down on his screen :
On networks with lots of devices connecting and disconnecting it can
make sense to lower the DHCP lease time to allow addresses allocated to
now dormant devices to be re-used sooner.

That makes sense, I did always wonder why the lease time was adjustable.

I use mainly fixed IP addresses - they have infinite leases. I have a
small pool of addresses for guests, and they have a lease time of 12
hours.

--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
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