Mailing List Archive

BGP scanner taking up CPU
Hi all,

We have a 6506 with Sup720-MSFC2 running IOS 12.2(18)SXD5. This router
holds the entire internet BGP table. Now we are suspecting the BGP
scanner process for causing temporary high CPU loads. Because this
process runs with a high priority, exec commands, pings and snmp seem no
to get through anymore. When using the vty exec, output seem to stall
for 1 to 3 seconds at least every minute.

Now we have already turned off any unnecessary commands using CPU (also
no logging console).

Now there is a command to tune how long a single process can claim the
cpu. This timer can be tuned with the process-max-time command. The
process-max-time is default 200 ms (and this is also the max). It can be
tuned down 20 ms.

Can anyone tell me if lowering this value could have a positive effect
on the CPU usage of the BGP scanner process?

One other thing that may be beneficial is to use next-hop
address-tracking (NHT). Available in IOS 12.3(14)T and up. I am not sure
if this feature is supported on 65xx sup720 (software advisor claims it
is not) and upgrading this router has a big impact. Anyone ever used
this feature on a 65xx sup720 and know of its impact on the BGP scanner?

Grtz,
Joris

_______________________________________________
cisco-nsp mailing list cisco-nsp@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/
Re: BGP scanner taking up CPU [ In reply to ]
Joris de Mooij <> wrote on Friday, August 11, 2006 2:11 PM:

> Hi all,
>
> We have a 6506 with Sup720-MSFC2 running IOS 12.2(18)SXD5. This router
> holds the entire internet BGP table. Now we are suspecting the BGP
> scanner process for causing temporary high CPU loads. Because this
> process runs with a high priority, exec commands, pings and snmp seem
> no to get through anymore. When using the vty exec, output seem to
> stall for 1 to 3 seconds at least every minute.

BGP Scanner is a low-priority process (check "show proc <pid>"), it
should not have that adverse effects. Maybe something else is going on.

> Now there is a command to tune how long a single process can claim the
> cpu. This timer can be tuned with the process-max-time command. The
> process-max-time is default 200 ms (and this is also the max). It can
> be tuned down 20 ms.
>
> Can anyone tell me if lowering this value could have a positive effect
> on the CPU usage of the BGP scanner process?

No, and we recommend not to tune the scheduler unless you know about the
side-effects.

> One other thing that may be beneficial is to use next-hop
> address-tracking (NHT). Available in IOS 12.3(14)T and up. I am not
> sure if this feature is supported on 65xx sup720 (software advisor
> claims it is not) and upgrading this router has a big impact. Anyone
> ever used this feature on a 65xx sup720 and know of its impact on the
> BGP scanner?

BGP scanner will still be around, but will no longer need to scan
everything and uses much lower CPU value. NHT is available in 12.2(33)SR
for the 7600..

best open a TAC case to find out why the router responds so slowly..

oli

_______________________________________________
cisco-nsp mailing list cisco-nsp@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/
Re: BGP scanner taking up CPU [ In reply to ]
On Fri, Aug 11, 2006 at 02:35:27PM +0200, Oliver Boehmer (oboehmer) wrote:
> Joris de Mooij <> wrote on Friday, August 11, 2006 2:11 PM:
>
> > Hi all,
> >
> > We have a 6506 with Sup720-MSFC2 running IOS 12.2(18)SXD5. This router
> > holds the entire internet BGP table. Now we are suspecting the BGP
> > scanner process for causing temporary high CPU loads. Because this
> > process runs with a high priority, exec commands, pings and snmp seem
> > no to get through anymore. When using the vty exec, output seem to
> > stall for 1 to 3 seconds at least every minute.
>
> BGP Scanner is a low-priority process (check "show proc <pid>"), it
> should not have that adverse effects. Maybe something else is going on.

Actually, those problems with BGP Scanner seem to be 6500-specific.
During BGP Scanner runs the box stops processing the CPU-switched packets
and the SPD queue on the RP owerflows - thus the SNMP, telnet (but even
e.g. software switched multicast) packets get dropped and "SPD flushes"
counters increment in jumps.

When SPD is disabled, the box runs much more smoothly, however manual
tuning of input hold-queues is needed for BGP etc.


With kind regards,

M.

--------------------------------------------------------------------------
---- ----
---- Marian Durkovic network manager ----
---- ----
---- Slovak Technical University Tel: +421 2 524 51 301 ----
---- Computer Centre, Nam. Slobody 17 Fax: +421 2 524 94 351 ----
---- 812 43 Bratislava, Slovak Republic E-mail/sip: md@bts.sk ----
---- ----
--------------------------------------------------------------------------
_______________________________________________
cisco-nsp mailing list cisco-nsp@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/
Re: BGP scanner taking up CPU [ In reply to ]
It would be interesting for someone to compare the
scanner CPU usage when they upgrade to 12.2(33)SRA that
has the fix for:

CSCef51906
BGP: reduce CPU impact of scanner

which is an internal enhancement we made to reduce the work
the scanner has to do.

Rodney

On Fri, Aug 11, 2006 at 02:56:20PM +0200, Marian Durkovic wrote:
> On Fri, Aug 11, 2006 at 02:35:27PM +0200, Oliver Boehmer (oboehmer) wrote:
> > Joris de Mooij <> wrote on Friday, August 11, 2006 2:11 PM:
> >
> > > Hi all,
> > >
> > > We have a 6506 with Sup720-MSFC2 running IOS 12.2(18)SXD5. This router
> > > holds the entire internet BGP table. Now we are suspecting the BGP
> > > scanner process for causing temporary high CPU loads. Because this
> > > process runs with a high priority, exec commands, pings and snmp seem
> > > no to get through anymore. When using the vty exec, output seem to
> > > stall for 1 to 3 seconds at least every minute.
> >
> > BGP Scanner is a low-priority process (check "show proc <pid>"), it
> > should not have that adverse effects. Maybe something else is going on.
>
> Actually, those problems with BGP Scanner seem to be 6500-specific.
> During BGP Scanner runs the box stops processing the CPU-switched packets
> and the SPD queue on the RP owerflows - thus the SNMP, telnet (but even
> e.g. software switched multicast) packets get dropped and "SPD flushes"
> counters increment in jumps.
>
> When SPD is disabled, the box runs much more smoothly, however manual
> tuning of input hold-queues is needed for BGP etc.
>
>
> With kind regards,
>
> M.
>
> --------------------------------------------------------------------------
> ---- ----
> ---- Marian Durkovic network manager ----
> ---- ----
> ---- Slovak Technical University Tel: +421 2 524 51 301 ----
> ---- Computer Centre, Nam. Slobody 17 Fax: +421 2 524 94 351 ----
> ---- 812 43 Bratislava, Slovak Republic E-mail/sip: md@bts.sk ----
> ---- ----
> --------------------------------------------------------------------------
> _______________________________________________
> cisco-nsp mailing list cisco-nsp@puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
_______________________________________________
cisco-nsp mailing list cisco-nsp@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/
Re: BGP scanner taking up CPU [ In reply to ]
Thanks for the input guys...

Grtz
Joris

-----Original Message-----
From: Rodney Dunn [mailto:rodunn@cisco.com]
Sent: vrijdag 11 augustus 2006 15:03
To: Marian Durkovic
Cc: Oliver Boehmer (oboehmer); cisco-nsp@puck.nether.net; Joris de Mooij
Subject: Re: [c-nsp] BGP scanner taking up CPU

It would be interesting for someone to compare the scanner CPU usage
when they upgrade to 12.2(33)SRA that has the fix for:

CSCef51906
BGP: reduce CPU impact of scanner

which is an internal enhancement we made to reduce the work the scanner
has to do.

Rodney

On Fri, Aug 11, 2006 at 02:56:20PM +0200, Marian Durkovic wrote:
> On Fri, Aug 11, 2006 at 02:35:27PM +0200, Oliver Boehmer (oboehmer)
wrote:
> > Joris de Mooij <> wrote on Friday, August 11, 2006 2:11 PM:
> >
> > > Hi all,
> > >
> > > We have a 6506 with Sup720-MSFC2 running IOS 12.2(18)SXD5. This
> > > router holds the entire internet BGP table. Now we are suspecting
> > > the BGP scanner process for causing temporary high CPU loads.
> > > Because this process runs with a high priority, exec commands,
> > > pings and snmp seem no to get through anymore. When using the vty
> > > exec, output seem to stall for 1 to 3 seconds at least every
minute.
> >
> > BGP Scanner is a low-priority process (check "show proc <pid>"), it
> > should not have that adverse effects. Maybe something else is going
on.
>
> Actually, those problems with BGP Scanner seem to be 6500-specific.
> During BGP Scanner runs the box stops processing the CPU-switched
> packets and the SPD queue on the RP owerflows - thus the SNMP, telnet
> (but even e.g. software switched multicast) packets get dropped and
"SPD flushes"
> counters increment in jumps.
>
> When SPD is disabled, the box runs much more smoothly, however manual
> tuning of input hold-queues is needed for BGP etc.
>
>
> With kind regards,
>
> M.
>
>
------------------------------------------------------------------------
--
> ----
----
> ---- Marian Durkovic network manager
----
> ----
----
> ---- Slovak Technical University Tel: +421 2 524 51 301
----
> ---- Computer Centre, Nam. Slobody 17 Fax: +421 2 524 94 351
----
> ---- 812 43 Bratislava, Slovak Republic E-mail/sip: md@bts.sk
----
> ----
----
> ----------------------------------------------------------------------
> ---- _______________________________________________
> cisco-nsp mailing list cisco-nsp@puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/

_______________________________________________
cisco-nsp mailing list cisco-nsp@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/