Negative caching on DNS

Today I have increased the SOA minimum TTL value to increase my negative caching period but I have seen that no DNS server respect my change:) Here are two different results;

From Google server 8.8.8.8

From another cache server:

What does this really mean? I thought, there must be a limitation somewhere and I checked RFC 2308 (Negative Caching of DNS Queries) but I don’t see any limitation although BIND documentation at zytrax.com says maximum value allowed by RFC is 3 hours, I couldn’t see any text saying this 🙁 I will dig later when I have more time…

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