RE: BGP and anycast

[Swede <ymanon () yahoo com>]

Thanks for the reply!

Well, I'm actually trying to "stretch" the rules of
unicast and go to anycast. The point is to have
several places on the internet replying to the same
addresses. I'll mirror the same services in these
places (on a /24 that is allowed through filters).

Masataka Ohta pointed me in this direction (you better
be quick, they seem to be about to expire)
* draft-ietf-dnsop-ohta-shared-root-server-00.txt
* draft-ietf-dnsop-hardie-shared-root-server-02.txt
If I understand these correctly I wasn't too fare away
on my first guess. *Except* that the "uniquely
routable addresses" should come from nearest upstream
(which mean they could be longer than /24).

Does anyone have any more pointers on this matter
(maybe examples on CCO :)?

Guess it's time to sign up on the lab reservation
list...
/Swede 

--- Mike Schoenecker <MSchoenecker () yipes com> wrote:
> If I understand this correctly you are trying to
> advertise one /24 out to 2
> separate providers on the internet.
> If this is the case you will need to make sure that
> the 2 providers in this
> scenario are the same and will allow you to
> advertise smaller subnets of
> this block.  If you advertise the same block out of
> 2 separate regions BGP
> will not know where to send traffic.  BGP will
> select the most specific and
> route to this destination.  If there are 2 similar
> advertisements there will
> be routing anomalies. If you are trying to connect
> the sites together [ one
> subnet ] across the internet, the best way to do
> this is to establish a VPN
> between sites and advertise the entire /24 out of
> one region and share the
> subnet between regions over the VPN.  The points of
> the VPN will need to be
> of public address space that is either advertised or
> routed to you from your
> provider.  Netscreen has a solution for this.  This
> will enable you to
> receive traffic destined to your network at one
> location and forward the
> necessary traffic across the internet to your other
> region over the VPN.  I
> have found it very difficult to get anyone to listen
> to advertisements less
> than a /24 this is why I suggest that the carrier
> between regions be the
> same it would be easier to get them to satisfy this
> request. I thought of
> the use of IBGP but you will still experience the
> same issues of
> reachability i.e the transit carrier would need to
> advertise no less than
> the /24.
>
> Hope this helps
> PS. get Internetwork Routing Architectures by Cisco
> it is the best book on
> BGP.
>
> -----Original Message-----
> From: owner-nanog () merit edu
> [mailto:owner-nanog () merit edu]On Behalf Of
> Swede
> Sent: Monday, January 29, 2001 5:18 PM
> To: nanog () merit edu
> Subject: BGP and anycast
>
>
>
> How does one announce the same net (with the same
> origin AS) from different places on the Internet? Or
> should the "anycast" networks be announced from
> different origin AS:es?
> (Can't find "anycast" setup in my BGP for
> Dummies<tm>)
>
> ----------------------------------------
> AS12345
> IGP
> (announces net 1.2.3/24 among others)
> Connected to several major networks (P, Q, W, Z)
> ----------------------------------------
> Isolated* site 1 (one unique routable net and
> 1.2.3/24)
> Router connected to a major network X, announced as
> AS12345
> ----------------------------------------
> Isolated* site 2 (one unique routable net and
> 1.2.3/24)
> Router connected to a major network Y, announced as
> AS12345
> ----------------------------------------
> * Isolated - No contact to main AS via IGP, tunnels
> or
> telepathy
>
> So when communicating among the sites (doing zone
> transfers etc) I use the unique routable network...
> piece of ca...
> ...but won't my BGP routers at the different
> locations
> be a bit puzzled when they see the announcements
> from
> another AS12345 for my unique networks (and more so
> for the anycast)?
> The config above does seem to break the concept of
> an
> AS.
>
> Feel free to bash my Yahoo mail if this post is
> utterly stupid or seems way out of scope
> /Swede - still among the clueless  aka Anders Plym,
> presently without *real* mail access





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