[PLUG] Local network routing mystery [SOLVED]

David Fleck dcfleck at protonmail.ch
Wed Dec 12 02:05:42 UTC 2018


Rebooting the router fixed the problem.

It's a Netgear genie 6200v2, with the original firmware, and getting a bit long in the tooth.  This is the first time that I remember it behaving oddly.

Thanks for the troubleshooting reminder.

--
- David Fleck

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, December 11, 2018 7:45 PM, Russell Senior <russell at personaltelco.net> wrote:

> Oh, also check to see that the IPaddr that your problematic laptop has is distinct from all other hosts on your network. I recall a problem once upon a time with the Paradyne/Zhone DSL modems that Integra Telecom used would happily hand out leases of ipaddrs that were already taken on the network, leading to periodic clashes with devices with static IPs.
>
> On Tue, Dec 11, 2018 at 5:42 PM Russell Senior <russell at personaltelco.net> wrote:
>
>> More info needed:
>>
>>   * What is the router? What is it running (i.e. stock vs 3rd party firmware);
>>   * Have you tried power cycling the router?
>>   * Have you looked at dmesg -T on your problematic laptop?
>>   * Have you looked at iptables on your problematic laptop?
>>
>> On Tue, Dec 11, 2018 at 5:32 PM David Fleck <dcfleck at protonmail.ch> wrote:
>>
>>> My wife and I have 2 practically identical ThinkPad laptops, both running OpenSUSE 42.3.  They connect to a wireless router via DHCP.  We also have several desktop machines (Linux & FreeBSD) with static IP addresses. All the machines are connected by a router.  Both laptops can see the router, the outside world, and each other.  But one laptop can see all the desktops, and the other one can't see any of them. The desktops can't see the one laptop, either.
>>>
>>> As far as I can see, the routing tables are the same on both laptops:
>>> m2:~ #  route  ### This is the non-connecting laptop
>>> Kernel IP routing table
>>> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
>>> default         192.168.1.1     0.0.0.0         UG    600    0        0 wlan0
>>> 192.168.1.0     *               255.255.255.0   U     600    0        0 wlan0
>>>
>>> dcf:~> route   ### This is the connecting laptop
>>> Kernel IP routing table
>>> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
>>> default         192.168.1.1     0.0.0.0         UG    600    0        0 wlan0
>>> 192.168.1.0     *               255.255.255.0   U     600    0        0 wlan0
>>>
>>> But when I try to ping from the non-connecting laptop:
>>> m2:~ # ping 192.168.1.9
>>> PING 192.168.1.9 (192.168.1.9) 56(84) bytes of data.
>>> ^C
>>> --- 192.168.1.9 ping statistics ---
>>> 5 packets transmitted, 0 received, 100% packet loss, time 3999ms
>>>
>>> whereas:
>>> dcf:~> ping 192.168.1.9
>>> PING 192.168.1.9 (192.168.1.9) 56(84) bytes of data.
>>> 64 bytes from 192.168.1.9: icmp_seq=1 ttl=64 time=9.59 ms
>>> 64 bytes from 192.168.1.9: icmp_seq=2 ttl=64 time=0.960 ms
>>> 64 bytes from 192.168.1.9: icmp_seq=3 ttl=64 time=0.960 ms
>>>
>>> I'm flummoxed. Everything I can think to look at on the non-connecting laptop looks right, but the machines simply don't 'see' each other, even though they can see other machines on the network and there is no difference in network topology distinguishing connecting and non-connecting machines. Reboots (of desktops and the laptop) haven't helped.
>>>
>>> Last data point: this was all working correctly 24 hours ago.
>>>
>>> --
>>> - David Fleck
>>> _______________________________________________
>>> PLUG mailing list
>>> PLUG at pdxlinux.org
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