Monitor traffic flow directions
NTA monitors traffic flow over interfaces on your network devices. On any selected device interface, network traffic can flow both into the device (ingress) and out from the device (egress). The header of any NTA view showing interface-level traffic provides a control that gives you the ability to choose the traffic direction you want to monitor. The traffic direction control gives you the following options for traffic flow monitoring:
- Both displays a summation of all traffic flowing both in and out of the selected node over the selected interface.
- Ingress displays only traffic flowing into the selected node over the selected interface.
- Egress displays only traffic flowing out of the selected node over the selected interface.
The size of ingress and egress packets is usually the same. However, it can differ for example if you have CBQoS policies defined for individual interfaces, and these policies define that certain packets are dropped and not delivered to the appropriate endpoint.
Consider the following scenario with two flows:
- Flow F1: PC1 (source) > the traffic of 86.7 MB is coming to the switch through interface if1 (ingress) and leaving the switch via interface if2 (egress) > PC 2 (destination)
- Flow F2: PC3 (source) > the traffic of 33.1 MB is coming to the switch through interface if3 (ingress) and leaving the switch via interface if2 (egress) > PC 2 (destination)
For PC2, NTA shows the following interfaces:
- if2 - the interface both flows (F1 and F2) use for leaving the switch (egress: 86.7+33.1=119.8 MB)
- if1 - the interface used by flow F1 for entering the switch (ingress: 86.7 MB)
- if3 - the interface used by flow F2 for entering the switch (ingress: 33.1 MB)