Hi Jon, If I personally saw it, I wouldn't bother since I would assume there would be a method to your madness. ;-) Jeff -----Original Message----- From: Gaynor, Jonathan [mailto:Jonathan.Gaynor@fccc.edu] Sent: Friday, August 21, 2009 10:58 AM To: nanog@nanog.org Subject: Redundancy & Summarization My institution has a single /16 spread across 2 sites: the lower /17 is used at site A, the upper /17 at site B. Sites A & B are connected internally. Currently both sites have their own ISPs and only advertise their own /17's. For redundancy we proposed that each site advertise both their own /17 and the whole /16, so that an ISP failure at either site would trigger traffic from both /17s to reconverge towards the unaffected location. My worry/question: will carriers down the line auto-summarize my advertisements into a single /16, resulting in a 'load sharing' while both sites are active? If you're a backbone carrier and you saw x.x/16 and x.x/17 (or x.x/16 and x.x.128/17) being advertised from the same peer would you drop the longer match? Regards and thanks, Jon Gaynor, Senior Network Engineer Fox Chase Cancer Center (215) 214-4267, jonathan.gaynor@fccc.edu