400 names the reason: a double quote (NDP strips it), the literal texts SPACE / EQUALQUOTE / EQUALINVALUE (they corrupt NDP's tokeniser), a character outside NDP's key or value class (NDP silently drops the option), or more than 2000 options on the row.{
"default-server": "string",
"option-name": "string",
"option-value": "string",
"default-description": "string"
}