Manual:PCC
Introduction
PCC matcher will allow you to divide traffic into equal streams with ability to keep packets with specific set of options in one particular stream (you can specify this set of options from src-address, src-port, dst-address, dst-port)
Theory
PCC takes selected fields from IP header, and with the help of a hashing algorithm converts selected fields into 32-bit value. This value then is divided by a specified Denominator and the remainder then is compared to a specified Remainder, if equal then packet will be captured. You can choose from src-address, dst-address, src-port, dst-port from the header to use in this operation.
per-connection-classifier= PerConnectionClassifier ::= [!]ValuesToHash:Denominator/Remainder Remainder ::= 0..4294967295 (integer number) Denominator ::= 1..4294967295 (integer number) ValuesToHash ::= src-address|dst-address|src-port|dst-port[,ValuesToHash*]
Example
This configuration will divide all connections into 3 groups based on source address and port
/ip firewall mangle add chain=prerouting action=mark-connection new-connection-mark=1st_conn per-connection-classifier=src-address,src-port:3/0 /ip firewall mangle add chain=prerouting action=mark-connection new-connection-mark=2nd_conn per-connection-classifier=src-address,src-port:3/1 /ip firewall mangle add chain=prerouting action=mark-connection new-connection-mark=3rd_conn per-connection-classifier=src-address,src-port:3/2
Notes
PCC is available in RouterOS since v3.24. This option was introduced to address configuration issues with load balancing over multiple gateways with masquerade
Previous configurations:
- ECMP load balancing with masquerade
- NTH load balancing with masquerade
- NTH load balancing with masquerade (another approach)
Application Example - Load Balancing
Consider the following network layout:
Quick Start for Impatient
Configuration export from the gateway router:
/ ip address
add address=192.168.0.1/24 network=192.168.0.0 broadcast=192.168.0.255 interface=Local
add address=10.111.0.2/24 network=10.111.0.0 broadcast=10.111.0.255 interface=wlan2
add address=10.112.0.2/24 network=10.112.0.0 broadcast=10.112.0.255 interface=wlan1
/ ip firewall mangle
add chain=input in-interface=wlan1 action=mark-connection new-connection-mark=wlan1_conn
add chain=input in-interface=wlan2 action=mark-connection new-connection-mark=wlan2_conn
add chain=output connection-mark=wlan1_conn action=mark-routing new-routing-mark=to_wlan1
add chain=output connection-mark=wlan2_conn action=mark-routing new-routing-mark=to_wlan2
add chain=prerouting dst-address-type=!local in-interface=Local per-connection-classifier=src-address,dst-address:2/0 \
action=mark-connection new-connection-mark=wlan1_conn passthrough=yes
add chain=prerouting dst-address-type=!local in-interface=Local per-connection-classifier=src-address,dst-address:2/1 \
action=mark-connection new-connection-mark=wlan2_conn passthrough=yes
add chain=prerouting connection-mark=wlan1_conn in-interface=Local action=mark-routing new-routing-mark=to_wlan1
add chain=prerouting connection-mark=wlan2_conn in-interface=Local action=mark-routing new-routing-mark=to_wlan2
/ ip route
add dst-address=0.0.0.0/0 gateway=10.111.0.1 routing-mark=to_wlan1 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=10.112.0.1 routing-mark=to_wlan2 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=10.111.0.1 distance=1 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=10.112.0.1 distance=2 check-gateway=ping
/ ip firewall nat
add chain=srcnat out-interface=wlan1 action=masquerade
add chain=srcnat out-interface=wlan2 action=masquerade
Explanation
Let's assume this configuration:
IP Addresses
/ ip address add address=192.168.0.1/24 network=192.168.0.0 broadcast=192.168.0.255 interface=Local add address=10.111.0.2/24 network=10.111.0.0 broadcast=10.111.0.255 interface=wlan2 add address=10.112.0.2/24 network=10.112.0.0 broadcast=10.112.0.255 interface=wlan1
The router has two upstream (WAN) interfaces with the addresses of 10.111.0.2/24 and 10.112.0.2/24. The LAN interface has the name "Local" and IP address of 192.168.0.1/24.
Policy routing
/ ip firewall mangle add chain=input in-interface=wlan1 action=mark-connection new-connection-mark=wlan1_conn add chain=input in-interface=wlan2 action=mark-connection new-connection-mark=wlan2_conn
First it is necessary to take care of router's traffic - we need to make sure that traffic will leave via same interface it was coming from. We will mark all incoming connections, to remember what was the interface.
add chain=output connection-mark=wlan1_conn action=mark-routing new-routing-mark=to_wlan1 add chain=output connection-mark=wlan2_conn action=mark-routing new-routing-mark=to_wlan2
Then we will assign proper routing-mark to the packets leaving the router.
add chain=prerouting dst-address-type=!local in-interface=Local per-connection-classifier=src-address,dst-address:2/0 \
action=mark-connection new-connection-mark=wlan1_conn passthrough=yes
add chain=prerouting dst-address-type=!local in-interface=Local per-connection-classifier=src-address,dst-address:2/1 \
action=mark-connection new-connection-mark=wlan2_conn passthrough=yes
Action mark-routing can be used only in mangle chain output and prerouting, but mangle chain prerouting is capturing all traffic that is going to the router itself. To avoid this we will use dst-address-type=!local. And with the help of the new PCC we will divide traffic into two groups based on source and destination addressees.
add chain=prerouting connection-mark=wlan1_conn in-interface=Local action=mark-routing new-routing-mark=to_wlan1 add chain=prerouting connection-mark=wlan2_conn in-interface=Local action=mark-routing new-routing-mark=to_wlan2
Then we need to mark all packets from those connections with a proper mark. As policy routing is required only for traffic going to the Internet, do not forget to specify in-interface option.
/ ip route add dst-address=0.0.0.0/0 gateway=10.111.0.1 routing-mark=to_wlan1 check-gateway=ping add dst-address=0.0.0.0/0 gateway=10.112.0.1 routing-mark=to_wlan2 check-gateway=ping
Create a route for each routing-mark
add dst-address=0.0.0.0/0 gateway=10.111.0.1 distance=1 check-gateway=ping add dst-address=0.0.0.0/0 gateway=10.112.0.1 distance=2 check-gateway=ping
To enable failover, it is necessary to have a routes that will jump in as soon as others will become inactive on gateway failure. (and that will happen only if check-gateway option is active)
NAT
/ ip firewall nat add chain=srcnat out-interface=wlan1 action=masquerade add chain=srcnat out-interface=wlan2 action=masquerade
As routing decision is already made we just need rules that will fix src-addresses for all outgoing packets. if this packet will leave via wlan1 it will be NATed to 10.112.0.2/24, if via wlan2 then NATed to 10.111.0.2/24