Hello Mayank,
you can reuse the same crypto map on the new wan interface.
You need also a new default route using the new interface.
you need to upgrade the peer ip address on the other side router:
other side router:
no crypto isakmp key yourkey address old-address
! first you remove old command to be
! able to reuse the key
crypto isakmp key yourkey address new-address
inside the crypto map do the following
crypto map name ipsec-isakmp
set peer new-address
no set peer old-address
Be aware that changes can be critical on HQ side: calling a non-existing ACL in a crypto map block causes a black hole in all following crypto map blocks because the non existing ACL works as a permit ip any any.
Hope to help
Giuseppe
