Ingress egress regress software#
If only using ingress flows, the NetFlow reporting software will show 100 bytes outbound, even if it was compressed to 50 bytes. Traffic compression with Cisco NetFlow means that what comes in 100 bytes might go out as 50 bytes. Why collect with egress, if ingress worked so well with NetFlow v5? Because hardware such as WAN optimizers compress data. Generally, it is used in combination with Ingress, but it doesn’t have to be. NetFlow v9 Egress is collected on traffic going out (i.e. What goes in must go out, right? Ya, usually. To figure out outBound traffic volume, ingress must be collected on all interfaces and the reporting software then displays outbound traffic.
NetFlow v9 Ingress is collected on traffic going into (i.e. IPFIX probably renamed it because when talking about egress flows, IN_BYTES is sort of misleading. One annoying area where IPFIX and NetFlow v9 differ is in the labeling of fields: NetFlow v9 has ‘IN_BYTES’ and IPFIX labels the same field ‘octetDeltaCount’. Other vendors, such as Adtran and Enterasys, support NetFlow v9. Nortel supports IPFIX, as does/did Avici, which is now Soapstone Networks, Inc. Many collectors that work with NetFlow v9 will puke when they receive IPFIX.
Although they are very similar, don’t let any company tell you they are exactly the same. In theory, ingress and egress should work the same in IPFIX, which is based on NetFlow v9, but they are certainly different. NOTE: Egress is only available in Cisco NetFlow v9 and not NetFlow v5. ingress might be interesting to some readers. Under the listed circumstances it is thus advisable to interprete these terms in their context.I’m doing some more work lately with Wireshark and Scrutinizer v7. Summary: we discussed the Ingress and Egress concepts in their historical development as well as in their implication within different network levels. In such usage, the L2 and 元 aspect of ports on the firewall (usually called under Cisco PIX-devices "outside" and "inside") is generally being neglected. In other words on the level of the corporate gateway or firewall the egress term is applied to the information from Intranet to Internet and ingress term signifies the information from Internet to the Intranet (the latter also known as corporate LAN). See further details on “Understanding Ingress and Egress on 元 Switches (Part 2)".Īnd at the very latest many people started using the words for edge routers / gateways, using egress term for all outgoing connection (from the perspective of the "insider", usually a LAN with private IP address scope, but not obligatory) and ingress for the incoming packets (i.e., from MAN or WAN). There physical ports and VLAN-ports mingled the straight understanding but the logic behind stayed the same – a bridged frame that has to cross-over VLANs is ingressing the source VLAN port and egressing the destination VLAN port. Later on the terms were applied on 元-enhanced switches which brought some troubles since there we have 元 packets (this means with additional IP header) that are being routed and not switched. So for example for a “client” switch port (called under Cisco "switchport mode access") belonging to a certain VLAN this header information had to be erased before egressing, whereas for a VLAN trunk port (i.e., switchport mode trunk) this header information had to be preserved by the egressing process. This concept was later needed to explain OSI L2 enhancements like VLAN and QoS where different tags were applied to the frame header and a decision had to be made from the switch, where exactly to add or strip them down. To summarize as a definition on L2 ports: ingress is incoming from an adjacent node, egress outgoing to an adjacent node. Then a frame - mind NOT a packet - from a PC1 to the switch port 1 is ingress and the same frame from 24 to PC2 is egress. First we had "dumb" L2 switches with only physical ports. There is no big philosophy when one keeps in mind that Ingress/Egress-terms were originally explaining OSI L2 features.
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There are numerous misunderstandings of the Ingress and Egress concepts when related to different OSI layers, so here is a brief overview:
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