How can I monitor a router or switcheur with zabbix??
I used to monitor the traffic of my routers through snmp interface.
You have to configure the snmp interface on your router, after that, create a host in zabbix, and then create the items (snmp items) of the host.
Here you'll find the complete manual of zabbix: take a look at section "Advanced SNMP monitoring"
http://www.zabbix.com/documentation/1.8/complete