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Community Member

Do I need new IP's for routing between ISP's?

Hi

I'm looking to move from our single ISP to a dual ISP. Now I'm quite new to this so my query might be a little basic.

Currently the IP block we have is tied to our ISP (ISP1) to which we run a bgp session (the ISP provides us a default route via bgp). Now I'd like to add a second different ISP (ISP2) that also runs bgp, how would I go about routing my current ISP1 IP's with ISP2 given that the IP block belongs to ISP1 although we have been assigned those blocks by ISP1?

Is there anything I need to do with RIPE or with getting an AS number?

Any insight would be appreciated.

Thanks

Dan

10 REPLIES

Re: Do I need new IP's for routing between ISP's?

HI Dan, [Pls Rate if HELPS]

The only option is to contact with RIPE and register for an AS Number for your Company and it also reserve certain Prefixes.

Then, the prefixes can be advertised to different ISP in a Multihoming concept.

The ISP can also provide the default as before with BGP even after with the AS Concept as said before.

Note: Once the AS are registered, donot forget to create a route object for the prefixes registered. Because some of the Level-1 ISP's donot accept the prefixes without having the route-object created and registered.

Refer link below describing your scenario:

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a008009456d.shtml

Hope I am informative.

Pls Rate if HELPS

Best Regards,

Guru Prasad R

Community Member

Re: Do I need new IP's for routing between ISP's?

Hi

Thanks for the reply.

Just so I understand what you said, you are saying I need to get an AS number from RIPE. However if I go ripe, ripe say that the best path is to get IP's from your ISP, but if I do that then that block is allocated to that ISP, how will ISP2 then advertise thos blocks if they belong to ISP1?

Thanks

Dan

Re: Do I need new IP's for routing between ISP's?

HI Dan, [Pls Rate if HELPS]

The IP Block provided by ISP-1 will not be advertised to ISP-2 and the vicerversa is also not possible.

Without having the own AS registered & available, running an Multihoming concept is not at all possible.

Address to the RIPE that you are a Company running so and so business and your requirement to run a Multihoming concept with 2" different service provider by having a registered AS with self owned prefixes. Note to mention how many IP Prefixes required for your Business.

Note: You need to currently own atleast some minimum bandwidth (eg:2/3 MB) with the ISP-1 to apply for an AS and Prefix Request.

In addition, talk to your current ISP and they can provide the more right path to approach RIPE.

Hope I am Informative.

Pls Rate if HELPS

Best Regards,

Guru Prasad R

Community Member

Re: Do I need new IP's for routing between ISP's?

Hi,

It's better to approach an LIR(typically an ISP) for your requirement of ASN/Prefixes.

(1)

http://www.ripe.net/info/faq/rs/general.html#1

(2) http://www.ripe.net/membership/maps/index.html

Community Member

Re: Do I need new IP's for routing between ISP's?

Ref: " Note: Once the AS are registered, donot forget to create a route object for the prefixes registered. Because some of the Level-1 ISP's donot accept the prefixes without having the route-object created and registered. "

Can you give a few cases where they deny unregistered objects please?

Re: Do I need new IP's for routing between ISP's?

Dan,

as far as i know in your case, to use multiple providers it's best to get your own PI (Provider Independent) space is IP addressing space allocated directly to you by RIPE so you can get your own AS number for BGP and advertise your addresses out to the internet through both providers without relying on your ISP's. If you have one address space from one IPS i dont think the other provider will advertise that address space for you because it doesnt belong to them.

Community Member

Re: Do I need new IP's for routing between ISP's?

Hi Farncisco,

Can't one approach a chosen LIR for this purpose (Both ASN and Prefixes)?

AFAIK, when it comes to Prefix allocation RIRs only do it for prefixes > /21.

Specially for enterprise multihoming scenarios /21 and higher are typically not required in my opinion and most of the time unjustifiable.

Please correct me if I'm wrong.

Thanks

Community Member

Re: Do I need new IP's for routing between ISP's?

Get an AS number and have ISP 2 advertise your assigned netblock from ISP 1.

ISP 1 would advertise it's own netblock (i.e. a /16) with your more specific customer block (i.e. a /24 within the /17), and ISP 2 would advertise your customer block (the /24) only.

Just make sure that your netblock is not smaller than a /24, else it will most likely get filtered out.

Here's a very insightful howto: http://www.equinix.com/pdf/whitepapers/BGP-MHing-HOWTO-whitepaper.pdf

Cheers,

Alex

Blue

Re: Do I need new IP's for routing between ISP's?

I agree with Francisco and Gurusadr.

In a multihomed environment that uses two different ISPs, the best practice is to use provider-independent IP addresses and a provider-independent public AS number.

HTH

Victor

Community Member

Re: Do I need new IP's for routing between ISP's?

While it might be easier to get PI space, he might not be able to justify its usage depending on the size of his network.

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