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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