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How do most people manage IP addresses on their LAN?



 
 
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  #21  
Old February 5th 19, 03:45 PM posted to uk.telecom.broadband
Java Jive
external usenet poster
 
Posts: 475
Default How do most people manage IP addresses on their LAN?

On 05/02/2019 14:34, Chris Green wrote:

The problem is that sometimes when I wander around the house with my
laptop and try to change from one SSID to another, DHCP fails
completely when I reconnect. I.e. I get a strong WiFi connection but
no IP address (and thus no connectivity). If I turn WiFi off (or the
laptop off) for several minutes then on turning on again everything
works perfectly but just a reset isn't long enough to clear the issue.
It's as if the DHCP server is ignoring the request because it thinks I
already have an IP, or something in between is doing similar. There's
seems to be some sort of timeout that clears things down.


It sounds to me as though you may not have set up your WiFi to cope with
roaming. The phrase I'm picking up on is "from one SSID to another".
If you wish to roam seamlessly about the house, you need both router and
access point to be set up with the same WiFi characteristics - SSIDs,
passphrase, etc. But before altering the AP's configuration to match
that of the router, it might be interesting to know what happens when
you do the following:

1) In any normal fashion that you do so, be in the router's WiFi range
(so that you are connecting to that rather than the AP), open a command
prompt with Administrator rights, and run:
IPConfig /All
You should see that the WiFi has an IP address in the correct range
being dispensed via DHCP from your router.

2) Leaving the command prompt open, move the laptop into the range of
the AP, so that only it can now provide connection. Again run:
IPConfig /All

3) It may well give identical output as previously, meaning that either
the system has not yet reacted to being out of range of the router's
SSID or that it has already acquired a connection via the AP - you can
check which by examining which SSID it is connected to - or it may
give a link-local IP address in the 169.254.*.* range which, of course,
is no good, but it's what happens when the laptop can't get an IP via
DHCP. If you now can't access the rest of the LAN, try running
IPConfig /Release
IPConfig /Renew
Hopefully the first command will junk the previous lease, including any
spurious Link Local address, and the second will now be able to obtain a
connection in the normal way.

Try the above and report back.
  #22  
Old February 5th 19, 06:05 PM posted to uk.telecom.broadband
Invalid
external usenet poster
 
Posts: 149
Default How do most people manage IP addresses on their LAN?

In message , Chris Green
writes
As mentioned in another thread I'm having problems managing DNS on my
LAN. This is more of a rant than a question but I'd still quite like
to know how other people manage things.

I have Plusnet FTTC (irrelevant to the current issue) and a Draytek
2860n router connecting our NAT'ed LAN to it. There are quite a few
'things' which I need to connect to at times on the LAN:-

Desktop PC
Laptop PC
Printer
Backup machine
Gigaset base station
Draytek router
Second router used as Access Point

So, I have been using dnsmasq running on a Raspberry Pi (another
system I need to get to!) to provide local DHCP and DNS. This has
worked well in the main *except* that domestic ADSL/VDSL routers often
have bugs which prevent them working properly when they are not
providing DHCP/DNS themselves. In particular I went through the
default Plusnet router, a couple of D-Link ones and a tp-link one
before getting the Draytek which (mostly) works when its DHCP is
turned off.

The question in the subject is - how do people just using the default
ADSL/VDSL router setup cope with connecting to other things on their
LAN? Do they just remember the numeric IP address and leave it at
that? With three or four machines *from* which I may want to connect
and eight or so things to connect *to* this apprach is getting on for
unmanageable in my case. Are there any other ways to do it?

Getting back to my current problem, I've been having rather strange
issues with DNS and DHCP especially when 'roaming' around the house
with my laptop so I decided to remove the Raspberry Pi running dnsmasq
and turn the Draytek's DHCP/DNS back on. Then try and use Draytek's
'LAN DNS' facility which is supposed to allow you to create up to 20
DNS names for systems on the LAN - it's a complete can of worms! I
think it's not playing nicely with systemd's DNS but I'm not quite
sure yet. Grrrrrrrr!!!!!!

Has anyone else got a neat solution for providing named access to
systems and devices on a small LAN?



I have about the same number of "servers" on my LAN that I need to
connect to. I simply create a hosts file
(C:\Windows\System32\drivers\etc) with the relevant entries in it. I
also set up the router DHCP to always assign the same IP address to
these specific devices.

It takes a bit of setting up in the first place (I did it about 15 years
ago) and is a slight hassle (editing and redistribution) when you add a
new server - but that doesn't happen to me very often.

Distribute the hosts file to all the devices that need it.

It then works.
--
Invalid
  #23  
Old February 5th 19, 07:44 PM posted to uk.telecom.broadband
Chris Green
external usenet poster
 
Posts: 206
Default How do most people manage IP addresses on their LAN?

Andy Burns wrote:
Chris Green wrote:

nowhere near as nice as my own dnsmasq DHCP/DNS
server. It's just that the router doesn't seem to play nicely with
that set up.


Can't think why the router should get upset because of some function it
*isn't* performing ...


Because (certainly in some cases) the firewall decides not to pass
things. I'm sure there's other things that might go wrong too.

--
Chris Green

  #24  
Old February 5th 19, 07:52 PM posted to uk.telecom.broadband
Andy Burns[_5_]
external usenet poster
 
Posts: 414
Default How do most people manage IP addresses on their LAN?

Chris Green wrote:

Andy Burns wrote:

Can't think why the router should get upset because of some function it
*isn't* performing ...


Because (certainly in some cases) the firewall decides not to pass
things.


I can see it might not work at all if e.g. DHCP requests/replies don't
get passed between different interfaces (I think I had a similar
firewall zones issue when adding a 'guest wifi' SSID on openWRT)

But I thought your complaint was that the router initially worked then
went flaky over time unless you kept dhcp/dns running, perhaps I
misunderstood?
  #25  
Old February 5th 19, 07:52 PM posted to uk.telecom.broadband
Chris Green
external usenet poster
 
Posts: 206
Default How do most people manage IP addresses on their LAN?

Java Jive wrote:
On 05/02/2019 14:34, Chris Green wrote:

The problem is that sometimes when I wander around the house with my
laptop and try to change from one SSID to another, DHCP fails
completely when I reconnect. I.e. I get a strong WiFi connection but
no IP address (and thus no connectivity). If I turn WiFi off (or the
laptop off) for several minutes then on turning on again everything
works perfectly but just a reset isn't long enough to clear the issue.
It's as if the DHCP server is ignoring the request because it thinks I
already have an IP, or something in between is doing similar. There's
seems to be some sort of timeout that clears things down.


It sounds to me as though you may not have set up your WiFi to cope with
roaming. The phrase I'm picking up on is "from one SSID to another".
If you wish to roam seamlessly about the house, you need both router and
access point to be set up with the same WiFi characteristics - SSIDs,
passphrase, etc. But before altering the AP's configuration to match
that of the router, it might be interesting to know what happens when
you do the following:

That *is* how I have it set up. I have my 'main' SSID set to 2860n,
the 2860 router provides that on channel 6 and the access point
provides it on channel 11. Both have the same password.

The problem occurs when I move from the access point to the 2860's
area, if/when I disconnect and reconnect I end up with no IP address.
If I don't disconnect and reconnect I remain connected to the access
point with a very poor signal. Moving in the other direction usually
seems to work OK.


1) In any normal fashion that you do so, be in the router's WiFi range
(so that you are connecting to that rather than the AP), open a command
prompt with Administrator rights, and run:
IPConfig /All
You should see that the WiFi has an IP address in the correct range
being dispensed via DHCP from your router.

2) Leaving the command prompt open, move the laptop into the range of
the AP, so that only it can now provide connection. Again run:
IPConfig /All

3) It may well give identical output as previously, meaning that either
the system has not yet reacted to being out of range of the router's
SSID or that it has already acquired a connection via the AP - you can
check which by examining which SSID it is connected to - or it may
give a link-local IP address in the 169.254.*.* range which, of course,
is no good, but it's what happens when the laptop can't get an IP via
DHCP. If you now can't access the rest of the LAN, try running
IPConfig /Release
IPConfig /Renew
Hopefully the first command will junk the previous lease, including any
spurious Link Local address, and the second will now be able to obtain a
connection in the normal way.

I'm linux based but I can do similar. As I said it tends only to
happen when moving from access point to router.

--
Chris Green

  #26  
Old February 5th 19, 08:33 PM posted to uk.telecom.broadband
Chris Green
external usenet poster
 
Posts: 206
Default How do most people manage IP addresses on their LAN?

Andy Burns wrote:

But I thought your complaint was that the router initially worked then
went flaky over time unless you kept dhcp/dns running, perhaps I
misunderstood?


The fundamental problem is when 'WiFi roaming' from access point to
main router. Either the client doesn't roam and remains attached to
the distant router with a very weak signal or it *does* roam but
doesn't get an IP address with the new connection.

--
Chris Green

  #27  
Old February 5th 19, 09:18 PM posted to uk.telecom.broadband
Andy Burns[_5_]
external usenet poster
 
Posts: 414
Default How do most people manage IP addresses on their LAN?

Chris Green wrote:

The fundamental problem is when 'WiFi roaming' from access point to
main router. Either the client doesn't roam and remains attached to
the distant router with a very weak signal or it *does* roam but
doesn't get an IP address with the new connection.


Not familiar with the Draytek, I assume they bridge the wired and wifi
interfaces, rather than route between them (i.e single subnet covering
both?) If they do routing instead might be an arp issue ...


  #28  
Old February 5th 19, 09:41 PM posted to uk.telecom.broadband
Graham J[_3_]
external usenet poster
 
Posts: 93
Default How do most people manage IP addresses on their LAN?

Chris Green wrote:

{snip]

I'm linux based but I can do similar. As I said it tends only to happen when moving from access point to router.


Each of these devices (router, access point) contain network switches. A
switch builds a table of the MAC addresses that are logically connected
to each physical port. So for the wired LAN ports on the router each
port will have a table of the devices that are accessible through that port.

Suppose a port is connected to another network switch. That port will
show the MAC addresses of all the devices connected to the second switch.

Similarly the WiFi connection in the router is a logical port, and will
have a table of all the devices connected to it either directly or via
an access point connected wirelessly.

If you break the connection between the router and a client device
anywhere along the connection path, and reconnect the device via another
path (as the OP does when roaming wirelessly) the MAC address tables in
the router and all the intermediate devices should update themselves
quickly - within a couple of seconds. Sadly some devices don't do this.

In particular I've seen problems where a Vigor router connects to an
Engenius wireless access point configured in bridge mode to a second
Engenius access point. A similar configuration using two Tranzeo
devices worked as expected.

If your access points have a management interface it may be possible to
view the MAC address table to see whether this is happening.

In Cisco-speak this is a CAM table, see:

https://www.packet6.com/cam-table-fu...ch-operations/

From this description if a device is moved completely away from one
switch to another device on the LAN the first switch may be slow to
update its table.


--
Graham J
  #29  
Old February 5th 19, 10:32 PM posted to uk.telecom.broadband
Graham J[_3_]
external usenet poster
 
Posts: 93
Default How do most people manage IP addresses on their LAN?

Java Jive wrote:

[snip]
****:-)*** When not supplying local DHCP, does not try itself to pass
stuff up to the ISP, but obviously must allow requests from the DNS
server that is presumed to be present on the LAN.

DrayTeks seem to fail on both counts.


I've configured several MS SBS servers in the past (up to about 2011),
where the server provides DHCP and DNS, and where the internet router is
on the same subnet - so the router would be configured to allow VPN
access. This so that the server could be rebooted and its ILO activity
monitored during boot; as well as allowing VPN access to client machines
on the LAN if the SBS server is down.

The router was a Draytek 2830, configured with no DHCP. I never saw any
problem in its use in this mode.

The SBS server was configured with DNS forwarders including the DNS of
the ISP providing the internet connection.

What problems do you see where you have a separate DHCP and DNS server
and the Draytek has its DHCP disabled? Do you specify the local DNS
server in the Draytek's LAN setup?

In the Drayteks I have seen the default firewall DoS setting, if
enabled, will sometimes stop DNS traffic passing through the router. I
forget what I changed, but I probably altered the blocking threshold.
This affects the simple use case where the router provides internet
access for just one PC, as well as more sophisticated configurations.

--
Graham J

  #30  
Old February 6th 19, 12:41 AM posted to uk.telecom.broadband
Java Jive
external usenet poster
 
Posts: 475
Default How do most people manage IP addresses on their LAN?

On 05/02/2019 22:32, Graham J wrote:

What problems do you see where you have a separate DHCP and DNS server
and the Draytek has its DHCP disabled?* Do you specify the local DNS
server in the Draytek's LAN setup?


It's true that I have no personal experience, so cannot comment
definitively, of using them in this mode, but see the OP for a start,
and ISTR reading about some other problem as well - I think some
device couldn't get DNS via WiFi - though I'd be hard put to find it
now, because it was long time ago (and newer firmwares may have fixed
the problem since).

In the Drayteks I have seen the default firewall DoS setting, if
enabled, will sometimes stop DNS traffic passing through the router.* I
forget what I changed, but I probably altered the blocking threshold.
This affects the simple use case where the router provides internet
access for just one PC, as well as more sophisticated configurations.


Perhaps that was it, though at the time the complainant never found a
solution.

 




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