set ns [new Simulator] 
 
$ns rtproto DV  
 
 
set tr [open out.tr w] 
set nf [open out.nam w] 
$ns trace-all $tr 
$ns namtrace-all $nf 
 
 
 
 
 
proc finish {} { 
      	global ns nf tr 
      	$ns flush-trace 
	close  $tr 
	close  $nf 
	exec nam out.nam & 
	exit 0 
		} 
 
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
 
 
 
$ns duplex-link $n0 $n1 1Mb 50ms DropTail 
$ns duplex-link $n1 $n2 1Mb 50ms DropTail 

 
 
set cbr0 [new Agent/CBR] 
$ns attach-agent $n0 $cbr0 
$cbr0 set packetSize_ 500  
$cbr0 set interval_ 0.01 
 
set null2 [new Agent/Null] 
$ns attach-agent $n2 $null2 
 
$ns connect $cbr0 $null2 
 
proc mydump {} { 
 global ns 
 set now [$ns now] 
 puts "Routing table at time $now" 
 $ns dump-routelogic-nh 
 $ns dump-routelogic-distance 
} 
 
$ns at 1.0 "$cbr0 start" 
$ns at 8.0 "$cbr0 stop" 
$ns rtmodel-at 3.0 down $n0 $n1 
$ns rtmodel-at 6.0 up $n0 $n1 
 
$ns at 2.9 "mydump" 
$ns at 3.01 "mydump" 
$ns at 3.03 "mydump"
$ns at 3.06 "mydump"
$ns at 5.8 "mydump" 
$ns at 6.01 "mydump"  
$ns at 10.0 "finish" 
 
 
 
$ns run