Re: [isp-bgp] BGP Multihoming tips

[Praful Jaded <praful_jd@...>]

Hey all,

Thanx for the replies. I have setup BGP multihoming
with ISP1 and ISP2 now. I am accepting provider routes
only and not the full routing table. I am pushing all
my outbound traffic to my preferred ISP1 using local
preference. For routes that are not in my routing
table, I have a default pointing to ISP1(lesser
administrative distance) and another default to ISP2
with higher admin distance.For inbound traffic towards
my AS, I am using AS-PATH prepend attribute so that I
prepend my AS 3 times towards ISP2.So when I check the
reachability to my AS on the route-servers,I see my 
network reachable via ISP1( because of shorter
AS-PATH).

I have checked the reachability from Sprint and Level3
looking glass. Earlier without the AS-PATH prepend,
Sprint chose ISP1 to reach my AS, whereas Level3 chose
ISP2. But now everything is coming in via ISP1.Thats
what I needed. Any fine tuning required, let me know

Vikram, when I check out for my 16x.x.x.x/24 network
in the looking glass, I see BGP entry for the /24
space and not the aggregate. So  I guess this suggests
my network is advertised out by ISP1 and ISP2 as /24.

Thanx 
Praful

--- vdadlaney@... wrote:
> Hi Praful,
> 
> Since you have PA(Provider Assigned) address space
> you would have to negotiate with one of your
> providers to advertise the more specific subnet
> since your address block is most probably part of an
> aggregate. This would give u backup but if you want
> to do loadsharing like u have mentioned than u would
> have to get both your providers to announce the more
> specific block for your subnet. (Depending on the
> provider they may do this.) This takes care of
> inbound loadsharing. As far as outbound loadsharing
> goes you could ask your ISPs for partial routes for
> their locally originated prefixes and have default
> routes configured for prefixes that lie beyond your
> directly connected ISP's. Apologize if my answer is
> incorrect and would appreciate it if someone could
> correct me if i am wrong. Thx
> Regards,
> 
> Vikram
> 
> 
> > Hi All,
> > 
> > I currently have to setup a network involving BGP
> > multihoming to two different ISPs. I have a /24 IP
> > space from ISP1 now.I would like to use it for my
> > network involving DMZ.I have two Cisco 7200
> routers
> > which will run IBGP between them and the ISP1
> > terminates on R1 and ISP2 on R2 running EBGP. I
> want
> > to have inbound and outbound traffic load shared
> > between the ISPs and redundancy when one ISP
> fails.
> > Suggest me some good BGP multihoming tuning tips
> and
> > what do I need to negotiate with my ISPs for
> better
> > reachability of my network in the internet ?
> > 
> > Since I have the PA ( Provider Assigned)  /24
> space
> > from ISP1 , how do I go forward with ISP2 to
> advertise
> > it . The two ISPs are peered directly.
> > 
> > Thank You
> > Praful
> > 
> > 
> > 
> > 	
> > 	
> > 		
> >
>
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