Bash remove section of string using sed

Use sed to remove lines starting at BEGIN and ending with END line markers.

$ cat myfile.txt
1
2
BEGIN IGNORE
4 this line should be ignored
5 and this should be ignored
6 ignore
7 ignore
8 ignore
END IGNORE
10
11
12
13
14
15

$ cat myfile.txt | sed '/BEGIN IGNORE/,/END IGNORE/d'
1
2
10
11
12
13
14
15