On 14/01/2019 12:23, Paul Tansom wrote:
** Tim <t...@xendistar.co.uk> [2019-01-13 16:39]:
On 13/01/2019 14:47, t...@ls83.eclipse.co.uk wrote:
Hi Ralph
On 13/01/19 11:31, Ralph Corderoy wrote:
Hi Tim,
I'll just ask lots of questions in the hope it strikes lucky.
I have a puzzling issue here, in that I can't see a laptop on my
network from my own computer (normally I can ssh into the laptop just
fine). Both are connected via Wifi. The laptop has a static IP.
So both Computer and Laptop are *only* connected by Wi-fi.
Yes.
Computer's
IP address is from the router's DHCP server. The Laptop's IP address is
static. Is that last one done by having the DHCP server always dish out
the same IP address for Laptop's MAC address, or the Laptop has it
configured directly? If the latter, does the DHCP server know to steer
clear of the static addresses when allocating dynamically?
IP addresses are from third machine (server), which is running dhcpd
dishing out addresses to Laptop and Computer. Laptop gets same IP
address 192.168.2.8 from its MAC address, Computer gets its from a pool,
192.168.2.205. The DHCP server pool is well clear of the static IP's.
Can Laptop see Computer, e.g. ping(1), when Computer can't see Laptop?
No.
All devices are on the same IP network, including the network mask?
Yes.
However, I can ssh into a third computer on the network
How is Third connected? Also Wi-fi only? Static or dynamic IP address?
Cabled, static IP 192.168.2.2.
and from there can ping (and ssh into) the laptop.
When Computer SSH's into Third, does w(1) show you've come from the
Computer IP address you expect? Does `arp' show Computer's MAC address
or that of an access point?
w(1) shows 192.168.2.205 as expected.
arp shows the MAC address of Computer, not an access point.
Can Laptop SSH into Third? Ditto above WRT w(1).
Haven't got SSH set up for SSH logins from Laptop to Third, although I
expect it to work as these machines can see each other on the network.
arp lists the laptop HWaddess as incomplete.
There's also ip-neighbour(8) that gives `ip neigh' to show the table,
and allows an entry to be added. When it's not working, you could try
explicitly adding an ARP table entry to Computer for Laptop and see if
that makes it work.
OK, tried
#ip neigh add 192.168.2.8 lladdr 00:24:d2:94:35:16 dev wlp1s0
RTNETLINK answers: File exists
Further tests:
Disconnecting both Computer and Laptop from the access point and then
reconnecting both to a different access point. Now Computer cannot see
Laptop /or/ Third computer. So disconnect Computer again and get
physically close to the access point. Reconnect and now can see both.
Repeat with original access point, ensuring in close proximity. Again
can now see Laptop and Third from Computer.
So looks like a poor Wifi signal on original connect may be a factor.
I have seen something similar previously in terms of getting an IP
address from the DHCP server. I appear to be connected to the network
but have no IP address assigned to Computer. I am using Network Manager
of XFCE and suspect that under weak Wifi conditions I'm only getting a
partial connection.
I have seen with some WiFi access point the have the "the lights are on but
nobody is an home" syndrome, they look like they are working (lights etc)
but seemed to get stuck in a loop, you can not talk to them you can not see
them they are either limited in what they do or just don't do it at all.
Turn the power off to them. wait 10 seconds and then turn it back on again
and everything works as normal. Is there a firmware update available for
your access point?
** end quote [Tim]
I see that sometimes with my access point. It seems to pass traffic fine on the
wired connections, and several existing wireless connections work fine, but new
ones and the odd existing one and indicate they are working, but completely
fail when it comes to actually using anything on the network. After a while
they stop picking up DHCP leases (likely beause my AP doesn't handle that as my
config is beyond its capabilities - or was historically). After a while (if I
leave it that long) other devices start failing to route traffic too.
I have found the same issue with my the Billion BiPAC 7800N, the replacement
Netgear WNDR3700, the next replacement TP-Link TL-WDR3600 and the current
Netgear WNDR3700 with OpenWRT installed (which is actually much better, but
still not perfect).
The Netgear was aimed at improving performance, but was replaced because there
were two features on it that I needed that couldn't be used at the same time
(from memory VPN and IPv6). The TP-Link was replaced because it seems that it
doesn't support IPv6 with the majority of ISPs in the UK (hard coded a /64 when
most supply a /56). I'm still working on IPv6 on OpenWRT. I've got a tunnel
with Hurricane Electric working, but not my native addresses from my ISP (I
must have a decent conversation with them to confirm their setup). Comparing to
the old Billion isn't helpful because that just had a tick box to enable IPv6
which 'just worked'!
Anyhoo, I've strayed off the original thread!
I am considering putting WRT on my router, have to say that I am
appalled at the level of ability in its standard firmware, ever heard of
a router that can not block a port.
If anybody has any stories regarding OpenWRT I would interested to hear them
Tim H
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