[admin@MikroTik] ip route> /ip address print
Flags: X - disabled, I - invalid, D - dynamic
# ADDRESS NETWORK BROADCAST INTERFACE
0 10.0.0.217/24 10.0.0.217 10.0.0.255 Public
[admin@MikroTik] ip route> add
creates new item with specified property values.
comment short description of the item
copy-from item number
disabled
distance
dst-address Destination
gateway Gateway
netmask Network mask
preferred-source Source address of packets leaving the router
[admin@MikroTik] ip route> add dst-address=192.168.0.0/16 gateway=10.0.0.2
[admin@MikroTik] ip route> add gateway=10.0.0.1
[admin@MikroTik] ip route> print
Flags: X - disabled, I - invalid, D - dynamic, J - rejected,
C - connect, S - static, R - rip, O - ospf, B - bgp
# DST-ADDRESS G GATEWAY DISTANCE INTERFACE
0 S 0.0.0.0/0 r 10.0.0.1 1 Public
1 S 192.168.0.0/16 r 10.10.10.2 1 Public
2 DC 10.0.0.0/24 r 0.0.0.0 0 Public
[admin@MikroTik] ip route> print detail
Flags: X - disabled, I - invalid, D - dynamic, J - rejected,
C - connect, S - static, R - rip, O - ospf, B - bgp
0 S dst-address=0.0.0.0/0 preferred-source=0.0.0.0 gateway=10.0.0.1
gateway-state=reachable distance=1 interface=Public
1 S dst-address=192.168.0.0/16 preferred-source=0.0.0.0
gateway=10.10.10.2 gateway-state=reachable distance=1
interface=Local
1 DC dst-address=10.0.0.0/24 preferred-source=10.0.0.217 gateway=0.0.0.0
gateway-state=reachable distance=0 interface=Public
[admin@MikroTik] ip route>
Description of the printout:
number - number assigned to the item in the list
flag - shows the status of the item
dst-address/netmask - destination address and network mask, where mask is number of bits in the subnet mask.
gateway - gateway host, that can be reached directly through some of the interface. You can specify multiple gateways separated by comma "," for equal cost multipath routes. See more information on that below.
gateway-state - shows the status of the next hop. Can be r (reachable) or u (unreachable).
preferred-source - source address of packets leaving the router via this route. Must be a valid address of the router, which is assigned to the router's interface, where the packet leaves. Default value is 0.0.0.0, i.e., it is determined at the time of sending the packet out through the interface.
interface - interface through which the gateway can be reached. If (unknown), then the gateway cannot be reached directly, or the route has been disabled.
distance - administrative distance of the route. When forwarding a packet the router will use the route with the lowest administrative distance and reachable gateway.
Equal Cost Multipath Routing
Equal cost multipath routing feature can be used for load balancing.
New gateway is chosen for new source/destination IP pair. This means that, for example, one FTP connection will use only one link, but new connection to different server will use other link. This also means that routes to often-used sites will always be over the same provider. But on big backbones this should distribute traffic fine. Also this has another good feature - single connection packets do not get reordered and therefore do not kill TCP performance.
Equal cost multipath routes can be created by routing protocols (RIP or OSPF), or adding a static route with multiple gateways. The routing protocols may create routes with equal cost automatically, if the cost of the interfaces is adjusted properly. For more information on using the routing protocols, please read the corresponding section of the Manual.
To create a static multipath route, specify the gateway argument in the form "gateway=x.x.x.x,y.y.y.y", for example:
[admin@MikroTik] ip route> print
Flags: X - disabled, I - invalid, D - dynamic, J - rejected,
C - connect, S - static, R - rip, O - ospf, B - bgp
# DST-ADDRESS G GATEWAY DISTANCE INTERFACE
0 S 192.168.1.0/24 r 192.168.0.50 1 Local
1 S 0.0.0.0/0 r 10.0.0.1 1 Public
2 DC 192.168.0.0/24 r 0.0.0.0 0 Local
3 DC 10.0.0.0/24 r 0.0.0.0 0 Public
[admin@MikroTik] ip route> set 0 gateway=192.168.0.50,192.168.0.51,10.0.0.17
[admin@MikroTik] ip route> print
Flags: X - disabled, I - invalid, D - dynamic, J - rejected,
C - connect, S - static, R - rip, O - ospf, B - bgp
# DST-ADDRESS G GATEWAY DISTANCE INTERFACE
0 S 192.168.1.0/24 r 192.168.0.50 1 Local
r 192.168.0.51 Local
r 10.0.0.17 Public
1 S 0.0.0.0/0 r 10.0.0.1 1 Public
2 DC 192.168.0.0/24 r 0.0.0.0 0 Local
3 DC 10.0.0.0/24 r 0.0.0.0 0 Public
[admin@MikroTik] ip route>
Note that you can specify more than two gateways in the route. Moreover,
you can repeat some routers in the list several times to do a kind of cost
setting for gateways.
Policy Routing
Policy routing is implemented using multiple routing tables and list of
rules that specify how these tables should be used.
The Policy Routing is implemented in the MikroTik RouterOS based on source and destination addresses of the packet and on the interface the packet arrives at the router.
Note! Policy routing will not function 'as desired' for packets originated from the router or masqueraded packets. It is because these packets have source address 0.0.0.0 at the moment when they are processed by the routing table. Therefore it is not possible to match masqueraded packets by source address with policy routing rule. You should use matching by flow together with packet marking instead.
When finding the route for a packet, the packet is matched against policy routing rules one after another, until some rule matches the packet. Then action specified in that rule is executed. If no rule matches the packet, it is assumed that there is no route to given host and appropriate action is taken (packet dropped and ICMP error sent back to the source).
If the routing table does not have a route for the packet, next rule after the one that directed to current table is examined, until either route is found, end of rule list is reached, or some rule with action drop or unreachable is hit.
This way it is good to have last rule say "from everywhere to everywhere, all interfaces, lookup main route table", because then gateways can be found (connected routes are entered in the main table only).
Action for the rule can be one of:
Policy routing rules are configured in /ip policy-routing rule menu
[admin@MikroTik] ip policy-routing rule> print Flags: X - disabled, I - invalid # SRC-ADDRESS DST-ADDRESS INTE... FLOW ACTION TABLE 0 0.0.0.0/0 0.0.0.0/0 all lookup main [admin@MikroTik] ip policy-routing rule>
After installation, there is one default rule, which says that routes for all packets should be looked up in the "main" table. Argument description:
src-address/mask - Source IP address/mask, where mask is number of bits in the subnet. For example, x.x.x.x/32 for the address x.x.x.x and the 32-bit netmask 255.255.255.255
dst-address/mask - Destination IP address/mask, where mask is number of bits in the subnet.
interface - Interface name through which the packet arrives. Should be 'all' for the rule that should match locally generated or masqueraded packets, since at the moment of processing the routing table these packets have interface name set to loopback.
flow - flow mask of the packet to be matched by this rule. The flow masks are set using '/ip firewall mangle'.
Routing tables can be created/deleted in the /ip policy-routing menu:
[admin@MikroTik] ip policy-routing> print Flags: D - dynamic # NAME 0 D main [admin@MikroTik] ip policy-routing>
There is always the table "main" - this one can not be deleted and its name can not be changed. The "main" table is routing table that can be changed by issuing commands in the /ip route menu.
A new table can be added:
[admin@MikroTik] ip policy-routing> add name=mt [admin@MikroTik] ip policy-routing> print Flags: D - dynamic # NAME 0 mt 1 D main [admin@MikroTik] ip policy-routing>
Routes in a routing table can be added/removed/changed in /ip policy-routing table _table-name_ menu, where _table-name_ is name of the table:
[admin@MikroTik] ip policy-routing> table mt [admin@MikroTik] ip policy-routing table mt> add dst-address=10.5.5.0/24 gateway=10.0.0.22 [admin@MikroTik] ip policy-routing table mt> print Flags: X - disabled, I - invalid, D - dynamic, R - rejected # TYPE DST-ADDRESS G GATEWAY DISTANCE INTERFACE 0 static 10.5.5.0/24 r 10.0.0.22 1 Public [MikroTik] ip policy-routing table mt>
The "main" table is the same as one in /ip route:
[admin@MikroTik] ip policy-routing> table main
[admin@MikroTik] ip policy-routing table main> print
Flags: X - disabled, I - invalid, D - dynamic, R - rejected
# TYPE DST-ADDRESS G GATEWAY DISTANCE INTERFACE
0 static 192.168.1.0/24 r 192.168.0.50 1 Local
1 static 0.0.0.0/0 r 10.0.0.1 1 Public
2 D connect 192.168.0.0/24 r 0.0.0.0 0 Local
3 D connect 10.0.0.0/24 r 0.0.0.0 0 Public
[admin@MikroTik] ip policy-routing table main>
[admin@MikroTik] ip policy-routing table main> /ip route print
Flags: X - disabled, I - invalid, D - dynamic, J - rejected,
C - connect, S - static, R - rip, O - ospf, B - bgp
# DST-ADDRESS G GATEWAY DISTANCE INTERFACE
0 S 192.168.1.0/24 r 192.168.0.50 1 Local
1 S 0.0.0.0/0 r 10.0.0.1 1 Public
2 DC 192.168.0.0/24 r 0.0.0.0 0 Local
3 DC 10.0.0.0/24 r 0.0.0.0 0 Public
[admin@MikroTik] ip policy-routing table main>
Commands to achieve this:
[admin@MikroTik] ip policy-routing> add name=from_net1; add name=from_net2 [admin@MikroTik] ip policy-routing> print Flags: D - dynamic # NAME 0 from_net1 1 from_net2 2 D main [admin@MikroTik] ip policy-routing>
[admin@MikroTik] ip policy-routing> table from_net1 add gateway=10.0.0.1 [admin@MikroTik] ip policy-routing> table from_net2 add gateway=10.0.0.2 [admin@MikroTik] ip policy-routing> table from_net1 print Flags: X - disabled, I - invalid, D - dynamic, R - rejected # TYPE DST-ADDRESS NEXTHOP-S... GATEWAY DISTANCE INTERFACE 0 static 0.0.0.0/0 A 10.0.0.1 1 Public [admin@MikroTik] ip policy-routing> table from_net2 print Flags: X - disabled, I - invalid, D - dynamic, R - rejected # TYPE DST-ADDRESS NEXTHOP-S... GATEWAY DISTANCE INTERFACE 0 static 0.0.0.0/0 A 10.0.0.2 1 Public [admin@MikroTik] ip policy-routing>
[admin@MikroTik] ip policy-routing> rule [admin@MikroTik] ip policy-routing rule> print Flags: X - disabled, I - invalid # SRC-ADDRESS DST-ADDRESS INTERFACE ACTION TABLE 0 0.0.0.0/0 0.0.0.0/0 all lookup main [admin@MikroTik] ip policy-routing rule> add src-address=1.1.1.1/32 action=lookup \ \... table=main [admin@MikroTik] ip policy-routing rule> add src-address=2.2.2.1/32 action=lookup \ \... table=main [admin@MikroTik] ip policy-routing rule> add src-address=1.1.1.0/24 action=lookup \ \... table=from_net1 [admin@MikroTik] ip policy-routing rule> add src-address=2.2.2.0/24 action=lookup \ \... table=from_net2 [admin@MikroTik] ip policy-routing rule> print Flags: X - disabled, I - invalid # SRC-ADDRESS DST-ADDRESS INTERFACE ACTION TABLE 0 0.0.0.0/0 0.0.0.0/0 all lookup main 1 1.1.1.1/32 0.0.0.0/0 all lookup main 2 2.2.2.1/32 0.0.0.0/0 all lookup main 3 1.1.1.0/24 0.0.0.0/0 all lookup from_net1 4 2.2.2.0/24 0.0.0.0/0 all lookup from_net2 [admin@MikroTik] ip policy-routing rule> move 0 4 [admin@MikroTik] ip policy-routing rule> print Flags: X - disabled, I - invalid # SRC-ADDRESS DST-ADDRESS INTERFACE ACTION TABLE 0 1.1.1.1/32 0.0.0.0/0 all lookup main 1 2.2.2.1/32 0.0.0.0/0 all lookup main 2 1.1.1.0/24 0.0.0.0/0 all lookup from_net1 3 2.2.2.0/24 0.0.0.0/0 all lookup from_net2 4 0.0.0.0/0 0.0.0.0/0 all lookup main [admin@MikroTik] ip policy-routing rule>
Here the rules #0 and #1 are needed to process correctly connections from the local networks to the local addresses of the router. Namely, the 'connected' routes from the main table should be used instead of using the default routes from table from_net1 or from_net2. Rules #2 and #3 will handle packets with destination other than locally connected networks.
Additional Resources
Recommended readings for guidelines on routing issues: