netdev - Re: Q: bad routing table cache entries

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Date:	Tue, 12 Jan 2016 16:52:39 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Stas Sergeev <stsp@...t.ru>, netdev <netdev@...r.kernel.org>
Subject: Re: Q: bad routing table cache entries

On 12.01.2016 16:34, Hannes Frederic Sowa wrote:
> On 29.12.2015 11:54, Stas Sergeev wrote:
>> Hello.
>>
>> I was hitting a strange problem when some internet hosts
>> suddenly stops responding until I reboot. ping to these
>> host gives "Destination Host Unreachable". After the
>> initial confusion, I've finally got to
>> ip route get
>> and got something quite strange.
>>
>>
>> Example for GOOD address (the one that I can ping):
>>
>> ip route get 91.189.89.237
>> 91.189.89.237 via 192.168.8.1 dev eth0  src 192.168.10.202
>>      cache
>>
>>
>> Example for BAD address (the one that stopped responding):
>>
>> ip route get 91.189.89.238
>> 91.189.89.238 via 192.168.0.1 dev eth0  src 192.168.10.202
>>      cache <redirected>
>
> I tried to understand this thread and now wonder why this redirect route
> isn't there always. Can you please summarize again why this shouldn't
> happen? It looks totally fine to me from the configuration of your
> router and the subnet masks.

Just an addendum:

In IPv6 a redirect is seen as a notification telling hosts, this new 
address is on the same link as you. I think this semantic is the same 
for IPv4, so we are informing you that in essence you are getting a /32 
route installed to your new interface and can do link layer resolving of 
the new host.

I do think this is valid and fine.

Bye,
Hannes