getting out of range error.

[Nital]

hi all,
i had one problem. i am trying to crate 10 nodes. in my tcl script declaration nn is set to 10

then i created nodes like this.
for { set i 0} { $i < $val(nn)} { incr i } {
      //here i created the nodes n_($i)
}
but when i run the script i got this error:

MAC_802_11: accessing MAC cache_ array out of range (src 14, dst 19, size 10)!
more 9 lines.
i don't know why my nodes are getting this index value i.e. 11 to 19
they should get it from 0 to 9

if someone  can help me please.
Nital