BGP need class C?

Unanswered Question
Apr 3rd, 2008
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I plan on being the 'redundant' link for a customer that has a class C assigned by the primary provider. I planned on just using a /30 to peer and advertise that I'll take his class C and route it to him at the other end of the /30.

The Boss was discussing the project at a recent conference and has told me that someone with ARIN suggested the customer would need a class C from each of the providers. Will I need to allocate an entire class C just to peer and get his primary C routed to him over my network in a failover? Sounds way wrong to me.


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Edison Ortiz Thu, 04/03/2008 - 07:01
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The 'peering' IP will be provided to you by the ISP provider. You will be advertising your LAN subnet, and Yes - most providers out there require that you only advertise a /24.

If they were to let consumers send out /30 /29 /28 and so on, can you imagine the size of the internet routing table?



Danilo Dy Thu, 04/03/2008 - 07:11
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I don't get the first sentence. You can't advertise the Class C that the Primary Provider assigned to the Customer. Because it belongs to the Primary Provider, it does not belongs to the Customer or to you.

I think the second sentence equates to this.

- The Primary and Secondary Provider will assign the Customer one Class C each.

- The Primary and Secondary Provider has to agree which Private ASN to allow the Customer to use.

However, I don't get to see the need for BGP in this case. The BGP is needed if the Customer has its own IP Block but no ASN and need to ride on the two ISPs ASN.



cuchara61 Thu, 04/03/2008 - 09:06
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Guess that wasn't clear :-)

I, being the 2nd provider, am his redundant ISP. Customer has his own ASN and a Class C that was provided by Sprint - his primary ISP.

BGP will be used so that if his Sprint connection is down, his Class C will route thru me. I will peer with his ASN and my uplink's (ATT) ASN.

I'm thinking I only need a /30 for the link from me to customer.

Danilo Dy Thu, 04/03/2008 - 09:19
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For the link, yes you are right for the /30.

But you still not supposed to advertise the Customer Class C because it belongs to SPRINT - unless SPRINT permits you to do that. Take note that it is not allocated solely to the customer from NIC (ARIN, RIPE, APNIC, LACNIC, AFRINIC). I also suspect that the ASN is a Private ASN.




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