Re: IXP BGP routing

[antonio at nambu.uem.mz]

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Hi,

The telco will be joining the IXP soon. So they will be connected to 
the ISP and their ISP's will also be connected to the IXP and telco.
Weird but true.
One of the things the ISP's will achieve with this is that their leased 
lines to the telco will not carry local traffic.
At the moment we are using private AS's and private IP for the IXP.

Cheers,



> On Tue, May 21, 2002 at 12:04:04PM +0100, Stephane Bortzmeyer wrote: >
> The problem is that he probably does not have access to the Telco's >
> routers... (The original message was about the selection of routes by
> > the Telco.)
> 
> In that case, I misread the posting. I thought the problem was that
> the ISPs were not chosing IXP routes, since they received the same
> routes from their upstream Telco via EIGRP.
> 
> Antonio, is the Telco also a member of the IXP? Does it want to peer
> with its own customers? That would be a very unusual situation.
> Upstreams never normally peer with their own customers for obvious
> commercial reasons.
> 
> I would expect the situation actually to look like this:
> 
>                                    --- ISP1 ---
>                                  /              \
>       Internet <---------- Telco ----- ISP2 --- IXP
>                                  \              /
>                                    --- ISP3 ---
> 
> In this case, there is no problem with the Telco choosing the right
> route, because nothing has changed as far as they are concerned.
> However, ISP1 wishes to exchange traffic with ISP2/ISP3 via the IXP,
> in preference to the route via the Telco.
> 
> This will be completely broken if ISP1/ISP2/ISP3 are all part of
> Telco's EIGRP cloud. That is because the ISPs want to have a different
> routing policy than the Telco. By definition, having a different
> routing policy means that they must be a different AS. Therefore the
> Telco and ISPs cannot be part of the same IGP cloud.
> 
> If the Telco *does* have its own connection into the IXP, I expect
> they would only be interested in peering with other providers who have
> their own independent Internet link (e.g. their own satellite
> connection)
> 
> So IMO, your approach should be first to decouple the Telco and ISP
> routing domains as described before.
> 
> At worst: you can make the boundary a router on your own premises,
> assuming that you have administrative control over that router. In
> other words:
> 
>                     EIGRP
>         <------------------------------->
>          ---- R ----------------------- RA --- RB ---- IXP
>          TELCO       leased line        CUSTOMER
> 
> Router RA is the Telco border, and RB is your own border. The link
> between the two is the demarcation point. RA and RB point static
> routes at each other (or talk eBGP). RB is part of your own IGP and
> iBGP clouds.
> 
> This solution would be particularly suitable if the router RA is
> installed and owned by the telco as part of their service. Otherwise,
> I would draw the boundary at the leased line, as described previously.
> 
> Regards,
> 
> Brian.



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Antonio Godinho
B.Sc., 
MCP, MCP+Internet, MCSE (Microsoft Certified Systems Engineer)
CCNA (Cisco Certified Network Associate)
Tel. +258-1-490860
Cell +258-82-300392


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