[AusNOG] CPU - when to upgrade

[Mike Everest]

Hi Rys,

With routerOS, throughput limitation due to cpu really only happens when it completely runs out (i.e. 100% utilisation) - when you hit 100, router can't keep up with incoming packets and so some packets begin to be dropped.  That can have a follow-on effect that TCP stream initiators will start to pare back the transmit rate accordingly so if your router is CLOSE to 100% but not quite, it can still indicate a throughput limit.  But 70% - 80% is not usually a problem for throughput.

Other actions as already suggested, like fastpath and/or review of firewall rule order can make a huge difference - even adding a 'permit established' at the top of the forward chain can make a massive difference if you don’t already have it ;)

Cheers!

Mike.

> -----Original Message-----
> From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Rhys
> Cuff (Latrobe I.T)
> Sent: Friday, 6 April 2018 11:44 AM
> To: ausnog at lists.ausnog.net
> Subject: Re: [AusNOG] CPU - when to upgrade
> 
> Hi Guys
> 
> Thanks very much for the responses.
> We are a very small wireless ISP (around 2000 customers) and run MikroTik
> router kit (I know I know...) I can see its normally firewall and routing
> process's that use most.
> Running around 300mbps on the routers in question.
> I can certainly upgrade, just wasn’t sure if it was worth it.
> MikroTik don’t have much kit that is small and runs 24v.
> 
> Thanks again
> 
> Rhys
> 
> 
> 
> 
> -----Original Message-----
> From: Graeme Allen [mailto:mail at graemeallen.com]
> Sent: Friday, April 6, 2018 11:22 AM
> To: Rhys Cuff (Latrobe I.T)
> Cc: ausnog at lists.ausnog.net
> Subject: Re: [AusNOG] CPU - when to upgrade
> 
> Hi Rhys,
> 
> If you are looking at an MRTG style graph, then as Jim points out you are
> probably looking at a 5 minute rolling average, and the peaks will very likely
> be much higher and yes possibly impacting performance.
> 
> For a more instant view of the CPU, do a "show proc cpu history", this will
> show you the spikes (assuming csco).
> 
> Assuming the box you are using is not just under-powered, you need to look
> at what is hitting the cpu and see if you can control/remove it.
> 
> Chasing "links that don't seem to go as hard as they should", oh man, that's
> such a can of subjective worms......
> 
> 
> On Fri, April 6, 2018 10:51 am, Jim Woodward wrote:
> > On 06-04-2018 10:21, Rhys Cuff (Latrobe I.T) wrote:
> >
> >
> > Hi Rhys,
> >
> >
> > If it's a Cisco I have found that once you start hitting 70% you'll
> > start to see Latency creep up, this in turn will likely to have an
> > overall effect on achievable speeds.
> >
> > If the 70% figure is an average then peaks may be quite a bit higher,
> > I would consider working on a plan to upgrade the device(s) or do the
> > usual process of looking at your configuration to see if you have any
> > misconfigured/redundant ACL's or or routing policies that may be
> > eating into your CPU performance.
> >
> > Kind Regards,
> >
> >
> > Jim.
> >
> >
> >> FROM: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] ON BEHALF OF
> >> Rhys Cuff (Latrobe I.T)
> >> SENT: Friday, April 6, 2018 10:19 AM
> >> TO: ausnog at lists.ausnog.net
> >> SUBJECT: [AusNOG] CPU - when to upfrade
> >>
> >>
> >> Hi Guys
> >>
> >>
> >> When you have a router and cpu is hitting about 60 - 70% with traffic
> >> load would that impact speeds?
> >>
> >> I've got a few links that don't seem to go as hard as they should,
> >> but I can't find the
> >> reason._______________________________________________
> >>
> > AusNOG mailing list
> > AusNOG at lists.ausnog.net
> > http://lists.ausnog.net/mailman/listinfo/ausnog
> >
> >
> 
> 
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