+----------------------------+
| 'e' | USE_EXCEPT |
|------+---------------------|
- | 'H' | HUB |
- |------+---------------------|
| 'I' | USE_INVEX |
|------+---------------------|
| 'K' | USE_KNOCK |
|------+---------------------|
| 'S' | OPERS_SEE_ALL_USERS |
|------+---------------------|
- | 'T' | IGNORE_BOGUS_TS |
- |------+---------------------|
| 'Z' | ZIPLINKS |
|------+---------------------|
| '6' | IPv6 |