anchor.diff:     RESOLVE
   ;
   
  +srt_retain
  +:
  +   RETAIN
  +;
  +
   srt_tag
   :
      TAG tag = DEC
  
positive.code:    NO_READVERTISE
  ;
  
  srt_passive
  :
     PASSIVE
  
negative.code:    | srt_next_hop
     | srt_next_table
     | srt_no_readvertise
     | srt_no_retain
     | srt_passive
     | srt_preference
     | srt_readvertise
     | srt_reject
     | srt_resolve
     | srt_retain
     | srt_tag
  ;
  
  