Ridwan BAngEt: Paket Flow in Mikrotik its very important

MikroTik RouterOS is designed to be easy to operate in various aspects of network configuration. Therefore creating limitation for individual IP or natting internal clients to a public address or Hotspot configuration can be done without the knowledge about how the packets are processed in the router - you just go to corresponding menu and create necessary configuration.

As it was impossible to get everything in one diagram, Packet flow diagram for Mikrotik RouterOS v3.x was created in 2 parts:

Bridging or Layer-2 (MAC) where Routing part is simplified to one “Layer-3″ box
Routing or Layer-3 (IP) where Bridging part is simplified to one “Bridging” box

Analysis

Basic Concepts

- starting point in packets way thought the router facilities. It does not matter what interface (physical or virtual) packet is received it will start its way from here.

- last point in packets way thought the router facilities. Just before the packet is actually sent out.

- last point in packets way to router itself, after this packet is discarded

- starting point for packets generated by router itself

Configurable Facilities

Each and every facilities in this section corresponds with one particular menu in RouterOS. Users are able to access those menu and configure these facilities directly
- /ip firewall connection tracking

- /ip firewall filter

- /ip firewall nat

- /ip firewall mangle

- /queue simple and /queue tree

- /ip ipsec policy

- /ip accounting

- /interface bridge settings - available only for traffic that go thought the bridge. For all other traffic default value is Yes

- /interface bridge filter

- /interface bridge nat

Automated processes and decisions

- check if the actual input interface is a port for bridge OR checks if input interface is bridge

- allow to capture traffic witch otherwise would be discarded by connection tracking - this way our Hotspot feature are able to provide connectivity even if networks settings are in complete mess

- bridge goes thought the MAC address table in order to find a match to destination MAC address of packet. When match is found - packet will be send out via corresponding bridge port. In case of no match - multiple copies of packet will be created and packet will be sent out via all bridge ports

- this is a workaround, allows to use “out-bridge-port” before actual bridge decision.

- router goes thought the route n order to find a match to destination IP address of packet. When match is found - packet will be send out via corresponding port or to the router itself . In case of no match - packet will be discarded.