[isp-bgp] Re: BGP path inconsistent with traceroute

["Thatte, Sachin" <SThatte@...>]

Pete,

Looks like you misunderstood my question, I do understand PHB of IP
routing and TTL expired response from a router could be from different.
My questions simply was is the next hop router route-views has BGP of
his own? 

thx for ur response
sachin
> -----Original Message-----
> From: Pete Templin [mailto:petelists@...]
> Sent: Tuesday, June 22, 2004 5:07 PM
> To: isp-bgp@isp-bgp.com
> Subject: [isp-bgp] Re: BGP path inconsistent with traceroute
> 
> 
> Thatte, Sachin wrote:
> > Can somebody shed light on the following issue?
> > 
> >> From route-views I see as-path best path for network
> >> 198.207.185.0/24 from as 3549 but the traceroute uses 701. Could it
> >> be because route-views uses ebgp-multihop and the actual IP
> >> next-hop router has bgp table of his own which is different than
> >> that of route-views?
> 
> Each BGP router has its own table.  This means several things:
> 
> 1) If at least one endpoint of your traceroute isn't located at 
> route-views, you might travel over a route completely different than 
> what route-views shows.
> 2) Routers perform destination-based forwarding.  At each hop 
> along the 
> way, the responding router forwards its response out its best 
> path back 
> to the source, so you're seeing the IP address of the 
> interface that the 
> packet is coming back from, not necessarily the IP address the packet 
> was forwarded to (but you are seeing the router the packet 
> was forwarded 
> to).
> 3) Likewise, each of those routers along the way has a unique 
> view back 
> to the source of the traceroute.  A traceroute that started 
> from within 
> 198.207.185.0/24 and headed to the point where you've been conducting 
> your traceroutes might follow a completely different path than what 
> you're seeing.
> 
> pt
> 
> 




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************************************************
ISPCON FALL 2004 - Santa Clara Convention Center
************************************************
      New Keynote Speakers just announced:
   Jeff Pulver, President & CEO of Pulver.com
Nigel Ballard, Wireless Director, Matrix Networks

 Use discount code EBF04 now and pay only $350!
      REGISTER TODAY at www.ispcon.com

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