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New Member

BGP AS

Customer has associated its web servers to Internet ISP's public ip addresses. they would like to be 24 / 7 operation. so they are looking for a redundant WAN link where via backup internet connection, web servers DNS entries could be sent out in the case primary router fails.

Question is

1.who gives out the BGP AS numbers?

2 should the client set up ibgp relationship between headend routers and ebgp with primary internet ISP router through the back up and primary internet link? 3.if the back up internet ISP is different from the Primary Internet ISP then the AS number that is given by Primary ISP- would it be recongnized by the back up ISP and would it let pass those Public ip addresses.

8 REPLIES

Re: BGP AS

Hello,

depending on where you are geographically located, you can get the AS number from the respective organization, for e.g. Europe, that is RIPE, check this link:

http://www.ripe.net/

As with regard to setting up iBGP and eBGP, you should indeed use iBGP between your redundant routers, and eBGP with the providers. In general, ISP's accept each others AS numbers.

HTH,

GNT

Re: BGP AS

Hi,

To explain this, some of BGP basic concepts should be explained.

In nut shell,

1) if the customer want to have a redundant internet link to the same ISP.

Then there is no need to involve BGP, ISP will take care about redundant routing in case of failure with primary link. similary in the customer, you can have static default routes to the alternate link to push the outbound traffic when the primary link fails.

2) if the customer would like to have redundant internet link via a different service provider, then ofcourse BGP needs to be involved.

In this case, the customer cannot continue to use the public ip address provider by the service provider 1. Because service provider 2 will not be able to route the traffic destined for ip addresses which are owned by service provider 1.

Hence in this case, the customer should register and gets its own IP Address space.

The standard norm is the minimum subnet a customer can register and get from the authority is a /24. With this, the customer will get his registered AS number.

Then the customer can run BGP with service provider 1 and service provider 2. He can agree up on certain policies both the service provider and run BGP, which will take care about dynamic routing..

There are some more ways also..

Let us know if this clarifies your doubt.

-VJ

New Member

Re: BGP AS

thanks for your input.

So the best practice would be to have two different ISP as it provides redundancy against an ISP failure as well as router failure.

The best case scenario would be to have two ISP and have own public ip address space.

- my client was told by the ISP that they would have to be a relatively big company to buy public space - if there are some restrictions regardig buying public ips then what are those limitations.

-if that is not an option then using the same internet isp with redundant links would simplify the problem with no BGP just simple IGP with default routes.

what would be the best possible solution (i know it is relative to what your needs are but how much flexibility and redundancy a small enterprize to achieve)

thanks in advance

Re: BGP AS

Hi,

Yes..Getting a separate IP subnet registered would be costly too.

For small enterprise, have redundant link to the same ISP, will be a good and easy/cost effective option to go with.

There are some multihoming hardware solution available in the market, using which you can have links from different ISP, but still have complete redundancy..

You can have a look in the internet by searching "multihoming internet device". You will get to know it :-)

Rate the post if it was helpful.

-VJ

Re: BGP AS

Hello,

in addition to Vijaya's post, also be aware that getting a public BGP AS requires good argumentation from you or from your client as to why you need it. Because there is only a limited number of AS's available, the numbering organizations are not giving them away without a provable need.

Apart from BGP, there are other ways to provide for redundancy, to one or more ISP's.

The basic rule should actually be to keep the connections as simple as possible, in your case, that could simply mean default staic routes with different administrative distances...

Regards,

GNT

Re: BGP AS

Hi,

Yes..Getting a separate IP subnet registered would be costly too.

For small enterprise, have redundant link to the same ISP, will be a good and easy/cost effective option to go with.

There are some multihoming hardware solution available in the market, using which you can have links from different ISP, but still have complete redundancy..

You can have a look in the internet by searching "multihoming internet device". You will get to know it :-)

Rate the post if it was helpful.

-VJ

Re: BGP AS

Hi,

Yes..Getting a separate IP subnet registered would be costly too.

For small enterprise, have redundant link to the same ISP, will be a good and easy/cost effective option to go with.

There are some multihoming hardware solution available in the market, using which you can have links from different ISP, but still have complete redundancy..

You can have a look in the internet by searching "multihoming internet device". You will get to know it :-)

Rate the post if it was helpful.

-VJ

New Member

Re: BGP AS

hi,

A query on the same.

Can I have a private AS number and run BGP with both the ISPs? The IP block used is acquired from one of the ISPs and advertised on both the ISPs.The primary ISP is chosen by the BGP policies set on the router. Is this possible?

Thanks in advance

Ashish

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