Could not set default value for ns3::Ipv4GlobalRouting::FlowEcmpRouting

[ws132...@gmail.com]

Hi，

   I run ns-3 (version 3.26) in my machine (Ubuntu 16.04 OS), but when i try to modify attribute of ipv4globalrouting, error occurs, just like that : msg="Could not set default value for ns3::Ipv4GlobalRouting::FlowEcmpRouting", file=../src/core/model/config.cc, line=779". Actually, I want to run ECMP in the simulation of fat-tree, the relative code is that " Config::SetDefault("ns3::Ipv4GlobalRouting::FlowEcmpRouting", BooleanValue(true)); ", and I run the code file with command " sudo ./waf --run scratch/Fat-Tree ".

anyone can give me some advices?

thank you in advance!