There is one more interesting problem. Let's, say, you install PC with ZEBRA and have all 120,000 prefixes. Internet is _internet_, sometimes people make a crazy things, and create a bad (misconfigured, or very long, or very unusual) announces. Some announces are fatal for Cisco IOS, some for Zebra, some for WellFleet (do someone remember it? Very big competitor -:)). Now, say, announce A crash Cisco IOS. 99.9% Internet backbones are Ciscos, so this announce breaks few Ciscos around and die - so you never know about it (and will not have a chance to be happy that _this announce crash Ciscos but do not crash ZEBRA). Not bad, of course - you are alive, all Internet is alive. Now, say, announce B crash ZEBRA (and do not crash Cisco). It will spread until it reach first ZEBRA on it;'s road - _your_ ZEBRA. So all Zerbras in Internet crash at once (and you are unhappy). It is not a joke - we had such scenario few years ago (it was 'gated vs Cisco and WellFreet vs Cisco'). And such scenario make Juniper back-bone a little dangerous (but I believe that JUNIPER debugged such problems long ago, so it is not a case today).