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Order of ASes in the BGP Path

  • From: Abhishek Verma
  • Date: Mon Aug 29 12:50:07 2005
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Hi,

Is the order of AS numbers (except for perhaps the first one which
denotes the AS the route was originated from) in the AS_PATH in BGP
important? In fact, does anybody even care for the first AS number
that appears in the Path?

AFAIK, AS numbers in the BGP serves two purposes. It helps in loop
detection and it helps us count the AS Path length.

If this is the case then the order should not really matter much.

My question is that whether the operators care if the order, for some
reason changes?

Eg.

Legend: {} denotes the sequence, while [] denotes the set

Path {1 2} [3 4] {5} 

Would somebody mind if this was represented as {1 2 5} [3 4] ?

Thanks,

Abhishek