[c-nsp] round-trip differences towards google

[Rodney Dunn]

If it's Cisco in the middle those packets in an equal cost routing
scenario, which is typical in the core for redundancy, will most likely
diverge to a different path due to the src/dst ip hashing.

The traceroute would show you if the paths diverge in the forward direction
but not in the reverse direction.

Rodney

On Wed, Jul 08, 2009 at 02:38:58PM +0200, Rens wrote:
> They both leave my network via the same IP transit but then afterwards some
> hops are different...
> 
> -----Original Message-----
> From: E. Versaevel [mailto:erik at infopact.nl] 
> Sent: mercredi 8 juillet 2009 12:45
> To: Rens
> Cc: 'David Freedman'; cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] round-trip differences towards google
> 
> Is there a difference when you traceroute with different source ip's ?
> 
> Rens schreef:
> > I expect the return routing to be the same as for all my IP addresses
> since
> > they are all advertised in the same way.
> > 
> > I guess google doesn't handle them the same way?
> > 
> > -----Original Message-----
> > From: cisco-nsp-bounces at puck.nether.net
> > [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of David Freedman
> > Sent: mercredi 8 juillet 2009 12:21
> > To: cisco-nsp at puck.nether.net
> > Subject: Re: [c-nsp] round-trip differences towards google
> > 
> > Rens wrote:
> >> Hi all,
> >>
> >>  
> >>
> >> I'm having some difficulties understand some round-trip difference on the
> >> same router just by changing the source interface:
> >>
> >>  
> > your source address will of course become the destination address which
> > google's equipment will want to send the ICMP replies back to, google's
> > return routing will dictate the path latency.
> > 
> > Dave.
> > 
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> 
> 
> 
> Erik Versaevel
> 
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