SED delete lines between two pattern matches

Question

I am trying to replace lines between two pattern/string matches using SED see below. I need to delete lines below interface GigabitEthernet0/3 up to inter

Answer 1

after posting I found my answer: here's my solution

cat somerouter.config | sed '/interface GigabitEthernet0\/3/,/interface GigabitEthernet0\/4/{/^interface GigabitEthernet0\/4/p;d;}' somerouter.config > somenewerrouter.config 

Then I just add back interface 0/3 with

sed -e '/interface\ GigabitEthernet0\/4/ i\
interface\ GigabitEthernet0\/3\
 description\ NOT USED\
 shutdown\
!' $filesw.tmp.1 > $filesw.tmp.2