Manual:Routing/OSPF

Summary

MikroTik RouterOS implements OSPF Version 2 (RFC 2328). The OSPF protocol is the link-state protocol that takes care of the routes in the dynamic network structure that can employ different paths to its subnetworks. It always chooses shortest path to the subnetwork first.

General

Sub-menu: /routing ospf

Properties

Property	Description
distribute-default (never | if-installed-as-type-1 | if-installed-as-type-2 | always-as-type-1 | always-as-type-2; Default: never)	specifies how to distribute default route. Should be used for ABR (Area Border router) or ASBR (Autonomous System boundary router) never - do not send own default route to other routers if-installed-as-type-1 - send the default route with type 1 metric only if it has been installed (a static default route, or route added by DHCP, PPP, etc.) if-installed-as-type-2 - send the default route with type 2 metric only if it has been installed (a static default route, or route added by DHCP, PPP, etc.) always-as-type-1 - always send the default route with type 1 metric always-as-type-2 - always send the default route with type 2 metric
metric-bgp (integer; Default: 20)	the cost of the routes learned from BGP protocol
metric-connected (integer; Default: 20)	the cost of the routes to directly connected networks
metric-default (integer; Default: 1)	the cost of the default route
metric-rip (integer; Default: 20)	the cost of the routes learned from RIP protocol
metric-static (integer; Default: 20)	the cost of the static routes
redistribute-bgp (as-type-1 | as-type-2 | no; Default: no)	redistribute all routes learned by the BGP protocol
redistribute-connected (as-type-1 | as-type-2 | no; Default: no)	redistribute all connected routes, i.e., routes to directly reachable networks
redistribute-rip (as-type-1 | as-type-2 | no; Default: no)	redistribute all routes learned by the RIP protocol
redistribute-static (as-type-1 | as-type-2 | no; Default: no)	if enabled, the router will redistribute the information about static routes added to its routing database, i.e., routes that have been created using the '/ip route add' command on the router
router-id (IP address; Default: 0.0.0.0)	the OSPF Router ID. If not specified, OSPF use one of router's IP addresses.

Notes

OSPF protocol supports two types of metrics:

type1 - external metrics are expressed in the same units as OSPF interface cost. In other words the router expects the cost of a link to a network which is external to AS to be the same order of magnitude as the cost of the internal links.

type2 - external metrics are an order of magnitude larger; any type2 metric is considered greater than the cost of any path internal to the AS. Use of type2 external metric assumes that routing between AS is the major cost of routing a packet, and eliminates the need conversion of external costs to internal link state metrics.

Monitor

Command /routing ospf monitor will display current OSPF status.

Available read only properties:

Property	Description
state (down | running)	shows if OSPF is running or not
router-id (IP address)	Router-ID chosen by OSPF.
dijkstras (integer)	shows how many times dijkstras were recalculated
db-exchanges (integer)
external-imports (integer)

Area

Sub-menu: /routing ospf area

Description

OSPF allows collections of routers to be grouped together. Such a group is called an area. Each area runs a separate copy of the basic link-state routing algorithm. This means that each area has its own link-state database and corresponding shortest path tree.

The structure of an area is invisible from other areas. This isolation of knowledge makes the protocol more scalable if multiple areas are used; routing table calculation takes less CPU resources and routing traffic is reduced.

However, multi-area setups create additional complexity. It is not recommended separate areas with fewer than 50 routers. The maximum number of routers in one area is mostly dependent on CPU power you have for routing table calculation.

Properties

Property	Description
area-id (IP address; Default: 0.0.0.0)	OSPF area identifier. An area with area-id=0.0.0.0 (the backbone) must always be present. The backbone always contains all area border routers. The backbone is responsible for distributing routing information between non-backbone areas. The backbone must be contiguous, i.e. there must be no disconnected segments. However, area border routers do not need to be physically connected to the backbone - connection to it may be simulated using a virtual link.
default-cost (integer; Default: 1)	specifies the cost for the default route originated by this stub area ABR. Applicable only for stub areas on ABRs
inject-summary-lsas (yes | no; Default: yes)	specifies whether to flood summary LSAs in this stub area. Applicable only for stub areas on ABRs
name (string; Default: )	the name of the area
translator-role (integer; Default: )	lalala
type (default | nssa | stub; Default: default)	area type

Status

Area Range

Sub-menu: /routing ospf area range

Description

Prefix ranges are used to aggregate routing information on area boundaries. By default, ABR creates a summary LSA for each route in specific area, and advertises it in adjacent areas. Using 'ranges' allows to create only one summary LSA for multiple routes and send only single advertisement into adjacent areas, or to suppress advertisements altogether. If a range is configured as 'advertise=yes', a single summary LSA is advertised for each range if there are any routes under the range is the specific area. Else ('advertise=no') no summary LSAs area created and advertised outside area boundaries at all.

Properties

Property	Description
advertise (yes | no; Default: yes)	whether to create summary LSA and advertise it to adjacent areas
area (string; Default: )	the OSPF area associated with this range
cost (integer | default; Default: default)	the cost of the summary LSA this range will create default - the largest cost of all routes used (i.e. routers that fall within this range)
range (IP prefix; Default: )	the network prefix of this range

Note

For an active range (i.e. one that has at least one OSPF route from the specified area falling under it), 'unreachable' route is created and installed in the routing table.

Network

Sub-menu: /routing ospf network

To start the OSPF protocol, you have to define the networks on which OSPF will run and associated area for each of these networks

Property	Description
area (string; Default: backbone)	the OSPF area to be associated with the specified address range
network (IP prefix; Default: )	the network prefix associated with the area. OSPF will be enabled on all interfaces that has at least one address falling within this range. Note that the network prefix of the address is used for this check (i.e. not the local address). For PtP interfaces this means the address of the remote endpoint.

Interface

Sub-menu: /routing ospf interface

Property	Description
authentication (none | simple | md5; Default: none)	specifies authentication method for OSPF protocol messages. none - do not use authentication simple - plain text authentication md5 - keyed Message Digest 5 authentication
authentication-key (string; Default: "")	authentication key to be used for simple or MD5 authentication
authentication-key-id (integer; Default: 1)	key id is used to calculate message digest (used only when MD5 authentication is enabled). Value should match on all OSPF routers from the same region.
cost (integer: 1..65535; Default: 1)	interface cost expressed as link state metric
dead-interval (time; Default: 40s)	specifies the interval after which a neighbor is declared as dead. This interval is advertised in hello packets. This value must be the same for all routers on a specific network, otherwise adjacency between them will not form
hello-interval (time; Default: 10s)	the interval between hello packets that the router sends out this interface. The smaller this interval is, the faster topological changes will be detected, but more routing traffic will ensue. This value must be the same for all routers on a specific network, otherwise adjacency between them will not form
interface (string | all; Default: all)	the interface name all - for all interfaces without specific configuration
network-type (broadcast | nbma | point-to-point | ptmp; Default: broadcast)	the OSPF network type on this interface. Note that if interface configuration does not exist, the default network type is 'point-to-point' on PTP interfaces, and 'broadcast' on all other interfaces. broadcast - network type suitable for ethernet and other multicast capable link layers. Elects designated router nbma - nonbroadcast multiacess. Protocol packets are sent to each neighbors unicast address. Requires manual configuration of neighbors. Elects designated router point-to-point - suitable for networks that consists only of two nodes. Does not elect designed router ptmp - Point-to-Multipoint. Easier to configure than NBMA because it requires no manual configuration of neighbor. Does not elect designed router. This is the most robust network type and as such suitable for wireless networks, if 'broadcast' mode does not works good enough for them
passive (yes | no; Default: no)	if enabled, do not send or receive OSPF traffic on this interface
priority (integer: 0..255; Default: 1)	router's priority. Used to determine the designated router in a broadcast network. The router with highest priority value takes precedence. Priority value 0 means the router is not eligible to become designated or backup designated router at all.
retransmit-interval (time; Default: 5s)	time between retransmitting lost link state advertisements. When a router sends a link state advertisement (LSA) to its neighbor, it keeps the LSA until it receives back the acknowledgment. If it receives no acknowledgment in time, it will retransmit the LSA
transmit-delay (time; Default: 1s)	link state transmit delay is the estimated time it takes to transmit a link state update packet on the interface

Status

NBMA Neighbor

Sub-menu: /routing ospf nbma-neighbor

Manual configuration for non-broadcast multi-access neighbors. Required only if interfaces with 'network-type=nbma' are configured.

Property	Description
address (IP address; Default: )	the unicast IP address of the neighbor
poll-interval (time; Default: 2m)	how often to send hello messages to neighbors which are in "down" state (i.e. there is no traffic from them)
priority (integer: 0..255; Default: 0)	assumed priority value of neighbors which are in "down" state

Virtual Link

Sub-menu: /routing ospf virtual-link

Description

As stated in OSPF RFC, the backbone area must be contiguous. However, it is possible to define areas in such a way that the backbone is no longer contiguous. In this case the system administrator must restore backbone connectivity by configuring virtual links. Virtual link can be configured between two routers through common area called transit area, one of them should have to be connected with backbone. Virtual links belong to the backbone. The protocol treats two routers joined by a virtual link as if they were connected by an unnumbered point-to-point network

Properties

Property	Description
authentication (none | simple | md5; Default: none)	specifies authentication method for OSPF protocol messages.
authentication-key (string; Default: "")	authentication key to be used for simple or MD5 authentication
authentication-key-id (integer; Default: 1)	lalala
neighbor-id (IP address; Default: 0.0.0.0)	specifies router-id of the neighbour
transit-area (string; Default: (unknown))	a non-backbone area the two routers have in common

Note

Virtual link should be configured on both routers. Virtual links can not be established through stub areas.

LSA

Sub-menu: /routing ospf lsa

Read only properties:

Property	Description
area (string)
type (string)
id (IP address)
originator (IP address)
sequence-number (string)
age (integerr)
checksum (string)
options (string)
body (string)

Neighbor

Sub-menu: /routing ospf Neighbor

Read only properties:

Property	Description
router-id (IP address)	neighbor router's RouterID
address (IP address)	IP address of neighbor router that is used to form OSPF connection
interface (string)	interface that neighbor router is connected to
priority (integer)	priority configured on neighbor
dr-address (IP address)	IP address of Designated Router
backup-dr-address (IP address)	IP address of Backup Designated Router
state (init | full | 2-way)
state-changes (integer)
ls-retransmits (integer)
ls-requests (integer)
db-summaries (integer)
adjacency (time)

OSPF Router

Sub-menu: /routing ospf ospf-router

Read only properties:

Property	Description
area (string)
router-id (IP address)
state (string)
gateway (IP address)
cost (integer)

Route

Sub-menu: /routing ospf route

Read only properties:

Property	Description
destination (IP prefix)
state (intra-area | inter-area | ext-1 | ext-2 | imported-ext-1 | imported-ext-2)
gateway (IP address)
interface (string)
cost (integer)
area (external | backbone)