Dear all, I modified ns2 code to support multiple interface according Ram¨®n Ag¨¹ero Calvo 's Document, but when i run script_ ,I meet following errors,I do not konw how to debug error in ns2 ? anyone could help me solve this problem ,I am very appreciate of you! num_nodes is set 50 INITIALIZE THE LIST xListHead can't read "tracefd": no such variable while executing "if { $tracefd == "" } {<BR>return ""<BR>}" (procedure "cmu-trace" line 4) invoked from within "cmu-trace Send "RTR" $self" (procedure "_o17" line 35) (Node/MobileNode add-target-rtagent line 35) invoked from within "$self add-target-rtagent $agent $port" (procedure "_o17" line 29) (Node/MobileNode add-target line 29) invoked from within "$self add-target $agent $port" (procedure "_o17" line 15) (Node attach line 15) invoked from within "$node attach $ragent [Node set rtagent_port_]" (procedure "_o3" line 78) (Simulator create-wireless-node line 78) invoked from within "_o3 create-wireless-node" ("eval" body line 1) invoked from within "eval $self create-wireless-node $args" (procedure "_o3" line 23) (Simulator node line 23) invoked from within "$ns_ node" ("for" body line 2) invoked from within "for { set i 0} { $i < $val(nn) } {incr i} {<BR> set node_($i) [$ns_ node]<BR>#set rt($i) [$node_($i) agent 255]<BR>#$rt($i) set-mac [$node_($i) set mac_(0)]<BR>$n..." (file "channel.tcl" line 82)