Networking: Would my SPAN setup on Cisco router create a switching loop?

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http://serverfault.com – I'd like to set up a SPAN [port-mirror] port on our main router. The router is a Cisco 2821. The goal is to be able to troubleshoot Internet issues at the packet level, and it won't happen that often. Here are the ports: GigabitEthernet0/0 - Connects to AT&T uplink equipment... some fiber converter box. GigabitEthernet0/1 - Connects to our Juniper firewall, then the rest of the network. FastEthernet0/0/0 ... FastEthernet0/1/3 - All of these FastEthernet ports are unused. I was considering keeping the cables where they are and assigning a FastEthernet port as a SPAN port, but Cisco's I (HowTos)