[c-nsp] IPv6 BGP Dual Homed dual site

[Terebizh, Evgeny]

Hi Scott 
My 2 cents. 
I guess you could advertise two /44s through eBGP sessions (one per each
site). In case one uplink goes down, you would advertise locally generated
/44 and /44 route learned through iBGP from another site. Basically,
router may advertise /44 from the neighboring site as soon as upstream ISP
withdraws this route (we can't advertise iBGP learned route to ISP cause
we have a best route through it).
You could configure a higher LOCAL_PREF for eBGP sessions to make sure
that inter site traffic is not going through the backdoor link in normal
scenario. 
I assume that return traffic won't go through the backdoor connection as
well, unless one of your uplink goes down.
Also I would use SoO community to prevent possible routing loops.
One more thing. I heard that there're some issues related to IPv6
multihoming. I guess you might check out existing RFCs for more details.

/ET



On 9/19/13 11:13 PM, "Scott Voll" <svoll.voip at gmail.com> wrote:

>I'm trying to wrap my head around the best way to setup BGP with IPv6
>
>We currently have two different ISP's connected to two different sites.
> then we run iBGP between the sites.
>
>so in an IPv4 world have a class C at each location.  then at each
>location
>my Firewalls NAT to the correct Class C as they exit my network.
>
>This way if the link between sites go down I'm not black holing the other
>sites because each site has it's own Class C it's announcing.
>
>Now if I have a single /40 and I'm subnetting it per location(eg /44), but
>all the other sites behind these sites are within that /40 how do I make
>sure I don't end up blackholing the other site(s)?  Does that make sense?
> Do I need to announce a /44 from each site?  if so, that will kill my
>meshed network(internal) if one site(external) goes down, or the WAN links
>go down.
>
>Thanks for any ideas.  Is there a best practice for this kind of setup?
>
>TIA
>
>Scott
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