I would have to agree....... Given that there are 2 European sites and 2
US sites, I think the overhead of BGP would be negligible, while at the same
time providing a graceful solution to a sticky problem. I think you stated
your point very well that, even tho the network may seem "small", the fact
there are multiple sites with redundant links makes the network more complex
like a "large" network, no matter how many actual routers, end PCs, etc.
Using BGP (eBGP treating the 2 networks on each continent as a different BGP
AS) would definitely make things simpiler to manage while giving more
control using routing policies and prefix lists. CCNP BSCN Question #1:
When to use BGP? (two of the possible answers) 1) When the flow of traffic
entering and leaving an AS must be manipulated. 2) When the AS has multiple
connections to another AS. Breaking the 2 London routers into an AS and the
two US routers into an AS, it seems to me being able to maniuplate the
routes between the 2 continents' ASes would be convenient and fits the
purpose of BGP very nicely. But also consider: CCNP BSCN Question #2:
When NOT to use BGP? (three of the possible answers) 1) Low bandwidth
between ASes. 2) Lack of memory/CPU power on those routers 3) A limited
understanding of BGP route filtering and selection. Kevin: What are the
speed of the links between New York/London and San Jose/London? Can the
routers at each site handle running BGP? Do you understand BGP and route
filtering? If the links aren't too tiny, the routers can handle it, and you
understand how to implement BGP route filtering, this BGP solution doesn't
sound bad to me........
My 2 cents.
Mike W.
"W. Alan Robertson" wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Peter,
>
> OSPF has a distance of 110, and yes, iBGP has a distance of 200. By
> having seperate routing domains for North America and Europe, he could
> use eBGP (Distance - 20) between his two networks.
>
> Distance wouldn't really do anything in this case, though, because
> European routes would not be learned via OSPF (Remember, we have
> theoretically split OSPF into two seperate routing domains, never the
> two shall meet).
>
> Instead, eBGP would be bridging the gap between the two OSPF networks.
> This would afford the opportunity to really take control of what
> routes were advertised between the two, and excercise strict control
> of the routing metrics, manipulating them in such a way as to ensure
> that the best path across the pond were utilized under all normal
> circumstances, but providing the redundant "less preferred" path in
> the event of some kind of outage.
>
> Can the same be accomplished via OSPF? Yes, but because we're dealing
> with Intra-area, and Inter-area routes, it may be more complex than by
> simply manipulating the link costs. Remember that OSPF chooses an
> Intra-area route with a Cost of 4,000,000 over an Inter-area route
> with a cost of 100. That's just one of the quirks of the protocol.
>
> As for "Why would you want to break up an AS that small into two
> seperate private ASes?", it's called thinking outside the box. We
> tend to think that a small network could not be better served by
> applying the same principles that we might use for a larger
> environment. Why is that? Instead of letting the number of devices
> determine the right solution (Or more properly, a good solution),
> let's form a solution based on the specific requirements.
>
> A network with a small number of devices, but consisting of multiple
> sites, and redundant links, presents a unique challenge. Forget the
> number of devices, and look at both the physical topology, and the
> problem that needs solving. BGPs powerful policy routing tools make
> it a good fit for this environment, when viewed from a requirements
> perspective.
>
> It's not the only solution, but it is a valid solution, and in my
> opinion, it's a good solution.
>
> Alan
>
> ----- Original Message -----
> From: "Peter I. Slow, CCNP Voice Specialist"
> To: "W. Alan Robertson" ;
>
> Sent: Tuesday, May 29, 2001 1:02 PM
> Subject: Re: Wanna Be a CCIE? Try This One [7:6076]
>
>
> > Absolutely, but he has traffic going from one router to another,
> it's not
> > ever exiting the system.
> > ...why would you want to break up an AS that small into two seperate
> private
> > ASes?
> > besides... the OSPF routes are going to take precedence, not that
> the admin
> > dist. cant be changed, but ospf is 120, and BGP int routes are
> 200....
> > (right?)
> >
> > ----- Original Message -----
> > From: "W. Alan Robertson"
> > To: "Peter I. Slow, CCNP Voice Specialist" ;
> >
> > Sent: Tuesday, May 29, 2001 12:42 PM
> > Subject: Re: Wanna Be a CCIE? Try This One [7:6076]
> >
> >
> > > Peter,
> > >
> > > With all due respect, he doesn't have an IGP problem... He has a
> > > routing problem, and would like the ability to influence the flow
> of
> > > traffic under certain circumstances to provide for better network
> > > performance.
> > >
> > > After hearing a better explanation of the real issue, path
> selection
> > > for an International site, the use of BGP might go a long way
> toward
> > > solving the issue.
> > >
> > > He could very simply address his issues by breaking his OSPF into
> two
> > > seperate routing domains, and utilizing BGP as a means of
> > > interconnecting them. He could manipulate the traffic through the
> use
> > > of something as simple as AS-path prepending, or the other
> mechanisms
> > > Chuck mentioned (local preference, weight, or meds).
> > >
> > > Routing protocols are but tools, a simple means to an end. Like
> all
> > > tools, each has it's strengths and weaknesses. Most important is
> that
> > > you select the right one for a given situation. In the absence of
> > > more information, the use of BGP sounds like a pretty good
> solution to
> > > the given problem.
> > >
> > > Alan
> > >
> > > ----- Original Message -----
> > > From: "Peter I. Slow, CCNP Voice Specialist"
>
> > > To:
> > > Sent: Tuesday, May 29, 2001 11:29 AM
> > > Subject: Re: Wanna Be a CCIE? Try This One [7:6076]
> > >
> > >
> > > > next time you recomend using bgp to fix an IGP problem, im going
> > > to.., well,
> > > > uh, just dont do it again.
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