How are nostro and vostro accounts reconciled?

Pretty much like any other account. You check against your own ledger what payments were due, and you will Credit/Debit Nostro the first time around (Credit in Nostro Account, Debit in your Ledger Account), and once transfers are done, Debit/Credit check again (Debit in Nostro, Credit in your Ledger account).

For transactions that are credited to the Nostro account, without having a Debit entry on your Ledger, then the transaction(s) need to be traced to find out from where the extra money came in, and vice versa, if the credit is less than what you were expecting, then you need to break down your aggregate ledger entries and see which ones were not posted.