Subnet Size for BGP peers.

Nathan Ward nanog at
Wed Jul 29 21:51:03 UTC 2009

On 30/07/2009, at 7:59 AM, Jim Wininger wrote:

> I have a question about the subnet size for BGP peers. Typically  
> when we
> turn up a new BGP customer we turn them up on a /29 or a /30. That  
> seems to
> be the "norm".
> We connect to many of our BGP peers with ethernet. It would be a  
> simple
> matter to allocate a /24 for connectivity to the customer on a  
> shared link.
> This would help save on some address space.
> My question is, is this in general good or bad idea? Have others  
> been down
> this path and found that it was a bad idea? I can see some of the  
> pothols on
> this path (BGP session hijacking, incorrectly configured customer  
> routers
> etc). These issues could be at least partially mitigated. Are there  
> larger
> issues when doing something like this or is it a practical idea?

What is your access network? Do you have a switch port per customer?
If so, look in to private VLANs on Cisco, or whatever similar feature  
exists for your vendor.

Nathan Ward

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