BGP and aggregation

In the referenced message, Austin Schutz said:

> Multiple ASNs wouldn't solve anything in this case. What was wanted was
> under normal circumstances both A and B only announce a /20, and when the
> link between A and B breaks announce more specifics. Multiple ASN =
> inconsistent AS.. no no.

  Not necessarily. If 'A' originates the aggregate route it can still be
transited via 'B', though with an additional AS hop. Not a perfect solution,
but then neither is running a gre tunnel.


The only perfect solution is having multiple internal paths which are
resilient to simultaneous outage. Failing that, I've never had a problem
with GRE. Back in 1994-1997 or so, I used them a lot for disconnected
sites, much as someone else mentioned, across sprint. Worked great
and was certainly cheaper than interlata circuits.