sudo apt-get install syslog-ng-core

source s_myrouter {
    udp(ip(0.0.0.0) port(514));
};

filter f_myrouter { host("192.168.1.1"); }; # replace with your router's IP address

destination d_myrouter { file("/var/log/myrouter.log"); }; # replace with where you want to log

log { source(s_myrouter); filter(f_myrouter); destination(d_myrouter); };

<Plugin snmp>
  <Data "if_Octets">
    Type "if_octets"
    Table true
    Values "IF-MIB::ifInOctets" "IF-MIB::ifOutOctets"
  </Data>
  <Host "tp-link">
    Address "192.168.0.1"
    Version 1
    Community "public"
    Collect "if_Octets"
    Interval 60
  </Host>
</Plugin>