[AusNOG] Cisco GRE Tunnel weirdness

Nathan Brookfield Nathan.Brookfield at simtronic.com.au
Fri Jan 3 18:08:47 EST 2014


When you were seeing this strangeness over the GRE, what was 'show proc cpu' looking like?

Kindest Regards,
Nathan Brookfield (VK2NAB)

Chief Executive Officer
Simtronic Technologies Pty Ltd

Local: (02) 4749 4949 | Fax: (02) 4749 4950 | Direct: (02) 4749 4951
Web: http://www.simtronic.com.au | E-mail: nathan.brookfield at simtronic.com.au




-----Original Message-----
From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Nathan Brookfield
Sent: Friday, 3 January 2014 6:08 PM
To: joe at apcs.com.au
Cc: ausnog at lists.ausnog.net
Subject: Re: [AusNOG] Cisco GRE Tunnel weirdness

It doesn't sound like an MTU issue to me that's for sure.... Hmmm!

Kindest Regards,
Nathan Brookfield (VK2NAB)

Chief Executive Officer
Simtronic Technologies Pty Ltd

Local: (02) 4749 4949 | Fax: (02) 4749 4950 | Direct: (02) 4749 4951
Web: http://www.simtronic.com.au | E-mail: nathan.brookfield at simtronic.com.au




-----Original Message-----
From: joe at apcs.com.au [mailto:joe at apcs.com.au]
Sent: Friday, 3 January 2014 6:06 PM
To: Nathan Brookfield
Cc: ausnog at lists.ausnog.net
Subject: Re: [AusNOG] Cisco GRE Tunnel weirdness

Not specifically iperf but I was able to send 1500byte ping request with df bit set, outside of the tunnel, with no issues. (1501 bytes failed)

This indicated to me that the path between the 2 sites should be OK. Let me know if you disagree?

On 2014-01-03 17:51, Nathan Brookfield wrote:
> It sounds like an issue with a hop in the path. Have you tried iperf 
> or similar tests outside of the tunnel to both end points?
> 
> Kindest Regards, Nathan Brookfield
> 
> Chief Executive Officer
> Simtronic Technologies Pty Ltd
> 
> Web: http://simtronic.com.au [1]
> Phone: 1300 592 330
> Fax: (02) 4749 4950
> 
>  On 3 Jan 2014, at 17:49, "joe at apcs.com.au" <joe at apcs.com.au> wrote:
> 
> Hi List,
> 
>  I have a GRE tunnel between 2 sites over a link limited to 1500 MTU.
> 
>  As such we have mtu set to 1440 and mss-adjust to 1400 on both ends.
> This is overly cautious probably but it was working.
> 
>  Anyway - it had been working quite fine for some time, but randomly 
> we started seeing massive performance issues. Bandwidth throughput 
> halved and ping times sky rocketed (~50ms to ~1000ms). We tried 
> bringing down the tunnel and back up, no luck, and even power cycled 
> each end (Cisco 3945's), no luck.
> 
>  We have confirmed that the config's had not been changed for weeks.
> Neither end had crashed and rebooted. The tunnel itself did not go 
> down between 'working' and 'not working'. Performance and ping times 
> via the tunnel endpoint address' is fine, proving (to me) that the 
> networks between the 2 sites are not the issue, but the tunnel itself.
> No links are saturated, and CPU performance is quite tame (both before 
> and during the issue)
> 
>  For now we have gone back to backup path but I haven't been able to 
> find similar problems online, and my own Cisco tunnel experience 
> leaves me empty so far.
> 
>  Has anyone experienced a similar issue? A working tunnel suddenly 
> having major performance issues?
> 
>  Thanks,
>  Joe
>  _______________________________________________
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>  AusNOG at lists.ausnog.net
>  http://lists.ausnog.net/mailman/listinfo/ausnog [2]
> 
> 
> Links:
> ------
> [1] http://simtronic.com.au
> [2] http://lists.ausnog.net/mailman/listinfo/ausnog
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