Re: [isp-bgp] BGP Multihoming tips

[Praful Jaded <praful_jd@...>]

Hi All,

I have setup BGP multihoming now. Thanx for all your
replies. Still I have few questions.I am accepting
only Providers routes from both ISPs.

1)Is it better to accept default routes from ISP1
(primary) and ISP2 (secondary) via BGP or

2)Point a default route to ISP1(lower admin
distance)and another one to ISP2( higher admin
distance).

Any problems with either ? 

I have implemented Option 2 now

Thanx,
Praful


--- vdadlaney@... wrote:

> Hi Praful,
> 
> The setup you have means that you are using ISP 2
> for backup only. Is that what u had originally
> intended or were the requirements changed due to
> some other factors. Just would like to know the
> thinking behind it in case i have to deal with this
> in the future. Thx
> 
> 
> > 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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