With awk:

$ servers='server1,server2,server3,server4,server5'

$ awk -v RS=, '{print NR "........" $0}' <<<"$servers"
1........server1
2........server2
3........server3
4........server4
5........server5

With awk:

$ servers='server1,server2,server3,server4,server5'

$ awk -v RS=, '{print NR "........" $0}' <<<"$servers"
1........server1
2........server2
3........server3
4........server4
5........server5

or, to output the line numbers with left-padding

awk -v RS=, '{printf "%3d........%s\n",NR,$0}' <<<"$servers"

(choose the field width 3 as appropriate for the size of your server list).