>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.
This question confuses running BGP, I think, with running BGP with
full routes. For a relatively small number of routes, OSPF is more
CPU intensive than BGP. OSPF hellos and such also consume more
bandwidth.
#3 is valid.
>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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