[ns] multicast problem

[Lee <yli@gpu.srv.ualberta.ca>]

Hi,

In a tcl script, there are

set ns [new Simulator -multicast on]
set mproto CtrMcast

set mrthandle [$ns mrtproto $mproto {}]
if {$mrthandle != ""} {
  $ns at 0.01 "$mrthandle switch-treetype 0x8002"
}

There is no other explicit multicast operation in the script.

However, I got the following problem.
Would you like to give me some clue why it happens? 
Thanks in advance.

Cheers,
Lee

ns: _o271 new-group 42 4294967040 -1 cache-miss: can't read
"protocols_(-1)": no such variable
    while executing
"$protocols_($iface) upcall $code $source $group $iface"
    (procedure "_o273" line 9)
    (mrtObject upcall line 9)
    invoked from within
"$mrtObject_ upcall $code $src $group $iface"
    (procedure "_o268" line 3)
    (Node new-group line 3)
    invoked from within
"$node_ new-group $src $group $iface $code"
    (procedure "_o271" line 3)
    (Classifier/Multicast new-group line 3)
    invoked from within
"_o271 new-group 42 4294967040 -1 cache-miss"