$ wget ftp://ftp.ncbi.nih.gov/genomes/Homo_sapiens/CHR_20/hs_ref_GRCh38.p12_chr20.fa.gz
--2019-01-23 07:54:51--  ftp://ftp.ncbi.nih.gov/genomes/Homo_sapiens/CHR_20/hs_ref_GRCh38.p12_chr20.fa.gz
           => ‘hs_ref_GRCh38.p12_chr20.fa.gz’
Resolving ftp.ncbi.nih.gov (ftp.ncbi.nih.gov)... 130.14.250.12, 2607:f220:41e:250::12
Connecting to ftp.ncbi.nih.gov (ftp.ncbi.nih.gov)|130.14.250.12|:21... failed: Connection timed out.
Connecting to ftp.ncbi.nih.gov (ftp.ncbi.nih.gov)|2607:f220:41e:250::12|:21... failed: Network is unreachable.
$