From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Ahern <dsahern@gmail.com>
Subject: Re: iproute2 - modifying routes in place
Date: Mon, 14 May 2018 14:20:10 -0600
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To: Ryan Whelan <rcwhelan@gmail.com>
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On 5/14/18 2:10 PM, Ryan Whelan wrote:
> On Mon, May 14, 2018 at 2:49 PM David Ahern <dsahern@gmail.com> wrote:
> 
>> On 5/14/18 12:40 PM, Ryan Whelan wrote:
>>> Same behavior:
>>>
>>>
>>> root@rwhelan-linux ~
>>> # ip -6 route
>>> ::1 dev lo proto kernel metric 256 pref medium
>>> fd9b:caee:ff93:ceef:3431:3831:3930:3031 dev internal0 proto kernel
> metric
>>> 256 pref medium
>>> fd9b:caee:ff93:ceef:3431:3831:3930:3032 dev internal0 src
>>> fd9b:caee:ff93:ceef:3431:3831:3930:3031 metric 1024 pref medium
>>> fe80::/64 dev enp0s3 proto kernel metric 256 pref medium
>>> fe80::/64 dev enp0s8 proto kernel metric 256 pref medium
>>> fe80::/64 dev internal0 proto kernel metric 256 pref medium
>>>
>>> root@rwhelan-linux ~
>>> # ip -6 route change fd9b:caee:ff93:ceef:3431:3831:3930:3032 dev
> internal0
>>> src fd9b:caee:ff93:ceef:3431:3831:3930:3031 metric 10
>>> RTNETLINK answers: No such file or directory
> 
>> 'change' only sets NLM_F_REPLACE. Since NLM_F_CREATE is not set ('ip ro
>> replace') it does not add a new route and expects one to exist. Your
>> table above shows the prefix with metric 256 not metric 10 so the route
>> does not match. You should be seeing a message in dmesg to this effect.
> 
> 
> Is there a syntax for changing a route in-place?  Specifically, i'm
> interesting in changing the metric of currently existing routes.
> 

No. Metric is one of the keys. You will need to insert and delete.