[quagga-users 14938] Re: Disable BGP general scanning, BGP SCAN-TIMER

bg at it-mark.net bg at it-mark.net
Fri Feb 16 22:21:45 GMT 2018

2018-02-16 04:12, William Herrin написав:

> On Thu, Feb 15, 2018 at 7:05 PM,  <bg at it-mark.net> wrote:
>> 2018-02-15 22:21, Alexis Rosen написав:
>>> On Feb 15, 2018, at 8:29 AM, bg at it-mark.net wrote:
>>>> But once every minute for about 3-10 seconds there is a "BGP general
>>>> scanning", which is arbitrarily executed on any of the processor 
>>>> cores and
>>>> loads it 100% within a specified time.
>> But can this idea be realized at all? Just by default, bgp-scan occurs 
>> every
>> minute and it can only be changed by specifying the interval from 5 - 
>> 60
>> seconds. And it seems that it's impossible to turn off this feature at 
>> all?
> The BGP scanner performs next-hop validation. Where the next hop is
> not your direct eBGP peer, the scanner is what figures out that routes
> are no longer reachable and picks new next-hops via which they are.
> If you have a trivial configuration where your BGP next hop is always
> your single, directly adjacent BGP peer, you can probably tweak the
> software to allow a longer timer and recompile it without ill effect.
> If you have more than one BGP router, multiple peers, or a multihop
> BGP configuration then you should probably leave well enough alone.
> If it's causing latency issues for other software on the server, you
> can consider running it with the "nice" command.

Thank you Bill for advice.

I thought there is a command that turns off the function bgp-scan. But 
you say that I need to recompile...
I solved the problem by transferring the bgpd process to a separate core 
(taskset command) and changing the priority using "nice".
The problem is resolved, only now the corresponding core is idle :) But 
this is not a problem yet.

But still the question. I have 4 bgp-neighbors in the "direct 
visibility" ethernet - for each bgp-connection there is a subnet /30, 
where is one ip - my router, other ip - bgp-neighbor. Does this 
configuration allow me to refuse the "bgp-scan" function in your 

> Regards,
> Bill Herrin

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