[ndnSIM] Global Routing Router work not well

[y]

Dear ndnSIM team 
  I'm using ndnSIM for a experiment,in my experiment,producer1 and producer2 have same prefix.when i print producer2's FIB the result is
prefix is/prefix
face is257cost is2
end node


prefix is/prefix
face is259cost is1
face is258cost is1
end node


prefix is/prefix
face is258cost is0
face is257cost is2
end node
The Producer node has two next hops，not one. I don't know why there is another hop in FIB.My code and topology file is:
        CommandLine cmd;
        cmd.Parse(argc, argv);
        AnnotatedTopologyReader topologyReader("", 25);
        topologyReader.SetFileName("src/ndnSIM/examples/topologies/2-1.txt");
        topologyReader.Read();
        std::string prefix = "/prefix";
        // Install NDN stack on all nodes
        ndn::StackHelper ndnHelper;
        ndnHelper.InstallAll();                                                                     
        ndn::StrategyChoiceHelper::InstallAll("/", "/localhost/nfd/strategy/best-route");
        ndn::GlobalRoutingHelper ndnGlobalRoutingHelper;
        ndnGlobalRoutingHelper.InstallAll();
        // Getting containers for the consumer/producer
        Ptr<Node> producer1 = Names::Find<Node>("p1");
        Ptr<Node> producer2 = Names::Find<Node>("p2");
        NodeContainer consumerNodes;
        consumerNodes.Add(Names::Find<Node>("c"));
        ndn::AppHelper consumerHelper("ns3::ndn::ConsumerCbr");
        consumerHelper.SetPrefix(prefix);
        consumerHelper.SetAttribute("Frequency", StringValue("10")); // 10 interests a second
        consumerHelper.Install(consumerNodes);
        ndn::AppHelper producerHelper("ns3::ndn::Producer");
        producerHelper.SetPrefix(prefix);
        producerHelper.SetAttribute("PayloadSize", StringValue("1024"));
        ndnGlobalRoutingHelper.AddOrigins(prefix, producer1);
        ndnGlobalRoutingHelper.AddOrigins(prefix, producer2);
        producerHelper.Install(producer1);
        producerHelper.Install(producer2);       
        // Calculate and install FIBs
        ndn::GlobalRoutingHelper::CalculateRoutes();



router


# node  comment     yPos     xPos
c	NA	1	1
r	NA	1	2
p1	NA	2	3
p2	NA	0	3


link


# srcNode   dstNode     bandwidth   metric  delay   queue
c   	        r	       10Mbps	   2	10ms	 20
r	            p1	       10Mbps	   2	10ms	 20
r	            p2	       20Mbps	   2	20ms	 20

Plesase tell me where is the problem. 
Thanks & Regards
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.lists.cs.ucla.edu/pipermail/ndnsim/attachments/20230912/541f4d74/attachment.html>