Recently I encountered an issue with subnet boundaries in SCCM 2007. Personally I rather not use subnet boundaries, but rather IP ranges or AD sites. In this case the client felt more comfortable with subnet, since they used them successfully in the past and did not want to change that. In preparation for a new location, boundaries needed to be put in SCCM and one of the boundaries was a supernet 10.129.0.0/19 (subnet mask 255.255.224.0). If you enter a this information in SCCM 2007, SCCM will create a subnet ID of 10.129.0.0 and treat this as a /24 range. See pictures below Making a /24 subnet (IP adress 10.129.0.1 – 10.129.0.254) instead left us short of a couple of subnets that are in the /19 subnet. In reality the supernet (/19 subnet) has 5 bits extra which make up 1+2+4+8+16 = 31 subnets (IP address 10.129.0.1 – 10.129.31.254). Needless to say that things did not work…

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