Chapter 45. Mirroring a network interface by using nmcli
Chapter 45. Mirroring a network interface by using nmcli Network administrators can use port mirroring to replicate inbound and outbound network traffic being communicated from one network device to another. Mirroring traffic of an interface can be helpful in the following situations: To debug networking issues and tune the network flow To inspect and analyze the network traffic To detect an intrusion Prerequisites A network interface to mirror the network traffic to. Procedure Add a network connection profile that you want to mirror the network traffic from: Attach a prio qdisc to enp1s0 for the egress (outgoing) traffic with the 10: handle: The prio qdisc attached without children allows attaching filters. Add a qdisc for the ingress traffic, with the ffff: handle: Add the following filters to match packets on the ingress and egress qdiscs , and to mirror them to enp7s0 : The matchall filter matches all packets, and the mirred action redirects packets to destination. Activate the connection: Verification Install the tcpdump utility: Display the traffic mirrored on the target device ( enp7s0 ): Additional resources How to capture network packets using tcpdump (Red Hat Knowledgebase)
nmcli connection add type ethernet ifname enp1s0 con-name enp1s0 autoconnect no nmcli connection modify enp1s0 +tc.qdisc "root prio handle 10:" nmcli connection modify enp1s0 +tc.qdisc "ingress handle ffff:" nmcli connection modify enp1s0 +tc.tfilter "parent ffff: matchall action mirred egress mirror dev enp7s0 " nmcli connection modify enp1s0 +tc.tfilter "parent 10: matchall action mirred egress mirror dev enp7s0 " nmcli connection up enp1s0 dnf install tcpdump tcpdump -i enp7s0