Re: BGP load balancing question

Hi Istong,

 Glad to know you've found a solution. But i don't quite understand how you
were able to achieve load sharing inbound. Please, kindly share your lab
config with explanations. Thanks.

Ifepe Okwudili.

On Thu, Jan 27, 2011 at 5:51 PM, istong <istong_at_stong.org> wrote:

> I labbed it up and then put it in production as it worked well in the lab.
> The outcome was as follows:
>
> routerA to ISPA
> routerB to ISPB
>
> routerA iBGP peers with routerB
>
> routerA and routerB are fed full BGP routes from their different ISP's
>
> The routers prefer different routes within BGP from each ISP for various
> reasons (AS path, egp vs igp, etc, etc. The net affect is about a 60/40
> split on both inbound and outbound traffic. That was the desired affect so
> that I can use both links from the ISP's, since I was maxing out the link
> when just using an active/standby routing solution using AS prepend and
> higher local pref on one router versus the other.
>
> The obvious remaining issue is if one link goes down the other will be
> overutilized. I'm ordering upgrades for both links to address that failure
> scenario :)
>
>
> Thanks for the input guys,
>
> Ian
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Narbik Kocharians
> Sent: Wednesday, January 26, 2011 11:31 AM
> To: Okwudili Ifepe
> Cc: Aaron; istong_at_stong.org; <ccielab_at_groupstudy.com>
> Subject: Re: BGP load balancing question
>
> It is possible to load share for a given prefix or bunch of prefixes
> when you have one router connecting to two different ISPs, but here you
> have
> two. Do these border routers connect to both ISPs?
>
> On Tue, Jan 25, 2011 at 11:49 PM, Okwudili Ifepe
> <okwudilic2003_at_gmail.com>wrote:
>
> > Hi Aaron,
> >
> > It would be nice if you could provide more information about your
> > topology. But from what i gather, in your AS, you have 2 border
> > routers connected to 2 different ISPs and you'd like to load balance
> > inbound and outbound traffic.
> >
> > I've thought about the scenario and i personally don't think it would
> > be possible to load balance outgoing traffic via bgp through any
> > manipulation of attributes as bgp always installs only one best route
> > to the ip routing table. Also, load balancing of inbound traffic from
> > two different ISPs in a real world implementation seems impossible as
> > both ISPs would be separated by multiple Autonomous Systems.
> >
> > If you have a solution to implementing such a scenario, i would
> > appreciate if you shared such information. I'm also studying for my
> > ccie lab and my opinion might not be the correct one. Thanks.
> >
> > Ifepe Okwudili.
> >
> >
> >
> >
> > On 1/22/11, Aaron <aaron1_at_gvtc.com> wrote:
> > > Equal cost 0/0 routing would seem to be sufficient for influencing
> > outbound
> > > traffic.... I believe accomplished with underlying Cef switching
> > mechanism
> > > (src/dst pair hash).... I think u just gotta get the dynamically
> learned
> > 0/0
> > > route into your igp... Would seem to save resources (bwidth/mem/CPU)
> too
> > > since you only maintain one route from SP.... that's outbound....
> Perhaps
> > > someone else can tackle inbound.... Been a while since I had my dual
> oc3s
> > to
> > > att and sprint .... Now I just have dual oc48s to single SP (att) less
> > > challenging I think with one ISP....can speak to that if you wish
> > >
> > > Aaron
> > >
> > > On Jan 22, 2011, at 10:30 AM, istong_at_stong.org wrote:
> > >
> > >> Hi,
> > >>
> > >> I have a scenario I'm looking at and wondering if anyone is
> > >> aware of any gotchas. I have two different ISP'sconencted
> > >> to two different boarder routers. The inside network
> > >> connects to the two border routers via BGP and learns
> > >> defaults routes from the routers (outbound traffic points to
> > >> the boarder routers via load balanced default routes). I'm
> > >> thinking about ways to get the traffic to load balance on
> > >> the wan links in and out.
> > >>
> > >> One thought is to have full routes sent to the border
> > >> routers and advertise internal routes out both border
> > >> routers to the ISP's. Then connect the border routers via
> > >> iBGP and exchange all routes. Lastly I would implement an
> > >> outbound as-path filter to only permit ^$ (to prevent
> > >> transit traffic).
> > >>
> > >> Any problems with the above scenario. I'm labbing it up but
> > >> hard to test without a lot of routes to simulate the ISP's,
> > >> etc.
> > >>
> > >>
> > >> Thanks
> > >>
> > >>
> > >>
> > >>
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>
> --
> *Narbik Kocharians
> *CCSI#30832, CCIE# 12410 (R&S, SP, Security)
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Received on Fri Jan 28 2011 - 09:18:41 ART