[AusNOG] VPLS OSPF question

[Tom Storey]

Whats wrong with using BGP internally. Isnt that what iBGP is for?


On 16 April 2013 10:34, Mitchell Warden <wardenm at wardenm.net> wrote:

> Hi Brad,
>
> Some ideas below. There are a lot of considerations...
>
> OSPF
> - Will run fine on a VPLS service. I've done this with up to 30 or so
> sites in the past and it works well.
> - 200 is a lot of sites - I would try to break it down to multiple smaller
> domains.
> - 50 routers in an area isn't a big deal. It will depend on the CPU and
> the number of updates, but even 200 is unlikely to be a problem.
> - 200 neighbour adjacencies however might be a big deal (they're all on
> the same broadcast domain). I think 200 is too many.
>
> BGP
> - All of the routers could be in the same subnet so they would be able to
> reach each other directly without an IGP, if you build neighbors with
> interface addresses instead of loopbacks.
> - You would need to use route reflectors to avoid having to mesh all 200
> routers.
> - I can't think of any reason BGP would reduce available bandwidth.
> - BGP isn't really designed to be used internally, and I would try to
> avoid using it that way.
> - BGP is probably better than OSPF if you can't reduce the size of the
> domain. It will be more scalable and probably more reliable.
>
> Cheers.
> Mitchell
>
>
> ----- Original Message -----
> From: Brad McGinn
> [mailto:the_xorach at yahoo.com]
> To: ausnog at lists.ausnog.net
> [mailto:ausnog at lists.ausnog.net]
> Sent: Tue, 16 Apr 2013 17:14:02
> +1000
> Subject: [AusNOG] VPLS OSPF question
>
>
> > Hi AusNog list,
>
> Long time listener, first or second time caller.
>
> I
> > know this list is pretty specific to Service Providers so I'm hoping any
> of
> > you who not only know carrier networks, but also have an insight into
> > enterprise networks maybe able to help me to get a view (or even help
> > understanding) of the pros and cons of running OSPF or BGP across a VPLS
> > network.
>
> I respectfully ask your advice.
>
> I am an enterprise
> > network engineer, not a service provider however I hope you don't hold
> that
> > against me.  We run OSPF in our Data Centre and BGP into a MPLS network
> > that all of our sites connect into.
>
> My fairly basic understanding of VPLS
> > is kind of like EoMPLS or even one big broadcast domain.  I assume any
> > IGP could potentially work across it but some factors must be taken into
> > consideration:  eg flapping sites, latency, reference bandwidth, DR/BDR
> > placement, multicast transmission and so on.
>
> So, with that in mind, I'm
> > wondering the following:
> -    would it be wise to run an IGP across a
> > VPLS backbone with over 200 sites? or would BGP be better? or even
> something
> > else?
> -    if an IGP is the go, would one use OSPF?
> -    if OSPF, do
> > you think it would be wiser to run a separate OSPF process for the VPLS
> > connected sites and a separate OSPF process for the DC?  and then
> > redistribute or just summarise right there? (so as to protect the DC from
> > OSPF recalculations when sites go up and down)
> -    if BGP would be the
> > go I'm wondering how one might go about it..  I know that all iBGP
> > neighbours must have a route to the peering IP of all other iBGP
> routers so
> > I would assume an IGP must be run anyway???
> -    cisco say that
> > anything more than 50 routers on an area is a bad idea, so if I have over
> > 200 sites potentially on the VPLS, will OSPF cut it?
>
> I guess i'm just
> > trying to get my head around the different technology.  I'd love to keep
> > the stability that BGP brings, but also would like to be able to make use
> > of the bandwidth that VPLS gives.
>
> Any hints or tips will be gratefully
> > received and thank you for any help.  If you would like to keep from
> > cluttering up subscriber's inboxes, please reply offlist.
>
> Again, thanks
> > for any help.
>
> Regards,
>
> Brad David
>
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