Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 732)

702 Multi-Service IronWare Switching Configuration Guide
53-1003036-02
The IP packet flow
19
The IP packet flow
Figure 187 shows how an IP packet moves through a Brocade device.
FIGURE 187 IP Packet flow through a Brocade device
Figure 187 shows the following packet flow.
1. When the Brocade device receives an IP packet, the Brocade device checks for IP ACL filters on
the receiving interface. If a deny filter on the interface denies the packet, the Brocade device
discards the packet and performs no further processing. If logging is enabled for the filter, then
the Brocade device generates a Syslog entry and SNMP trap message.
2. If the packet is not denied, the Brocade device checks for Policy Based Routing (PBR). If the
packet matches a PBR policy applied on the incoming port, the PBR processing is performed
and either drops the packet or forwards it to a port, based on the route map rules.
3. If the incoming packet does not match PBR rules, the Brocade device looks in the hardware IP
routing table to perform IP routing. The hardware routing table is pre-loaded with the complete
routing table, except for the directly connected host entries. Default and statically defined
routes are also pre-loaded in the hardware routing table. If the incoming packet matches a
route entry, the packet is routed according to the information provided in the route entry. The
ECMP and LAG load balancing is done by the hardware, if needed, to select the outgoing port.
4. If there is no match in the IP routing table and a default route is not configured, the packet is
dropped. For an IP packet whose destination IP address is to a directly connected host, the first
packet is forwarded to the CPU. If the ARP is resolved and the host is reachable, the CPU
creates a route entry in the hardware to route subsequent packets in hardware.