Manual:Routing/BGP
Applies to RouterOS: v3, v4
Summary
The Border Gateway Protocol (BGP) allows setting up an interdomain dynamic routing system that automatically updates routing tables of devices running BGP in case of network topology changes.
MikroTik RouterOS supports BGP Version 4, as defined in RFC 1771 -> RFC 4271
Standards and Technologies:
- RFC 4271 Border Gateway Protocol 4
- RFC 4456 BGP Route Reflection
- RFC 1965 Autonomous System Confederations for BGP
- RFC 1997 BGP Communities Attribute
- RFC 2385 TCP MD5 Authentication for BGPv4
- RFC 3392 Capabilities Advertisement with BGP-4
- RFC 2918 Route Refresh Capability
- RFC 2858 Multiprotocol Extensions for BGP-4
- RFC 2545 Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing
Instance
Sub-menu: /routing bgp instance
| Property | Description |
|---|---|
| as (integer: 0..4294967295; Default: ) | 32-bit BGP autonomous system number |
| client-to-client-reflection (yes | no; Default: yes) | in case this instance is a route reflector: whether to redistribute routes learned from one routing reflection client to other clients |
| cluster-id (IP address;) | in case this instance is a route reflector: cluster ID of the router reflector cluster this instance belongs to. This attribute helps to recognize routing updates that comes from another route reflector in this cluster and avoid routing information looping. Note that normally there is only one route reflector in a cluster; this case 'cluster-id' does not need to be configured and BGP router ID is used instead |
| confederation (integer: 0..4294967295;) | in case of BGP confederations: autonomous system number that identifies the [local] confederation as a whole |
| confederation-peers (integer: 0..4294967295;) | in case of BGP confederations: list of BGP peers internal to the [local] confederation |
| ignore-as-path-len (yes | no; Default: no) | whether to ignore AS_PATH attribute in BGP route selection algorithm |
| name (string;) | BGP instance name |
| out-filter (string;) | the output routing filter used by all BGP peers belonging to this instance |
| redistribute-connected (yes | no; Default: no) | if enabled, this BGP instance will redistribute the information about connected routes, i.e., routes to the networks that can be directly reached |
| redistribute-ospf (yes | no; Default: no) | if enabled, this BGP instance will redistribute the information about routes learned by OSPF |
| redistribute-other-bgp (yes | no; Default: no) | if enabled, this BGP instance will redistribute the information about routes learned by other BGP instances |
| redistribute-rip (yes | no; Default: no) | if enabled, this BGP instance will redistribute the information about routes learned by RIP |
| redistribute-static (yes | 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 BGP Router ID (for this instance). If not specified, BGP will use one of router's IP addresses. |
| routing-table (string; Default: ) | Name of routing table this BGP instance operates on.
Nondefault routing-table and list of VRFs cannot be configured for the same instance instance at the same time. Available starting from v4.3 |
| vrf (string;) | List of VRFs used for vpnv4 routes |
Peer
Sub-menu: /routing bgp peer
| Property | Description |
|---|---|
| address-families (ip | ipv6 | l2vpn | l2vpn-cisco | vpnv4; Default: ip) | list of address families about which this peer will exchange routing information. The remote peer must support (they usually do) BGP capabilities optional parameter to negotiate any other families than IP |
| allowas-in (string;) | |
| as-override (yes | no;) | If set, then all instances of remote peer's AS number in BGP AS PATH attribute are replaced with local AS number before sending route update to that peer. Happens before routing filters and prepending. |
| default-originate (always | if-installed | never;) | specifies how to distribute default route |
| hold-time (time; Default: ) | specifies the BGP Hold Time value to use when negotiating with peers.
According to the BGP specification, if router does not receive successive KEEPALIVE and/or UPDATE and/or NOTIFICATION messages within the period specified in the Hold Time field of the OPEN message, then the BGP connection to the peer will be closed. The minimal hold-time value of both peers will be actually used (note that the special value 0 or 'infinity' is lower than any other values)
|
| in-filter (string;) | name of the routing filter that is applied to the incoming routing information |
| instance (string;) | the instance this peer belongs to |
| interface (string | unspecified; Default: unspecified) | if specified, then outgoing connection will be made using only this interface; important if you want to run BGP using IPv6 link-local addresses |
| max-prefix-limit (integer;) | maximum number of prefixes to accept from a specific peer. When this limit is exceeded, TCP connection between peers is tear down |
| max-prefix-restart-time (time 1 minute .. 10 days | infinity; Default: infinity) | minimum time interval after which peers can reestablish BGP session.
|
| multihop (yes | no; Default: no) | specifies whether the remote peer is more than one hop away. This option affects outgoing nexthop selection as described in RFC 4271 (for EBGP only, excluding EBGP peers local to the confederation). It also affects
|
| name (string;) | the name of the peer |
| nexthop-choice (default | force-self | propagate; Default: default) | Affects the outgoing NEXT_HOP attribute selection. Note that nexthops set in filters always takes precedence. Also note that nexthop is not changed on route reflection, expect when it's set in filter.
|
| out-filter (string;) | name of the routing filter that is applied to the outgoing routing information, if instance has also configured out-filter, then first will be applied instance filters and only then peer's filters. |
| passive (yes | no;) | If set to yes, then connection attempts to remote peer are not made. The remote peer must initialize connection in this case. Available starting from v4.3 |
| remote-address (IP address;) | address of the remote peer |
| remote-as (integer: 0..4294967295;) | 32-bit AS number of the remote peer |
| remote-port (integer; Default: 179) | Remote peers port to establish tcp session |
| remove-private-as (yes | no; Default: ) | If set, then if BGP AS PATH attribute contains only private AS numbers, the attribute is removed before sending out route update. The removing happens before routing filters are applied and before local AS number is prepended to the AS path. Available starting from v4.3 |
| route-reflect (yes | no; Default: no) | specifies whether this peer is route reflection client |
| tcp-md5-key (string;) | key used to authenticate the connection with TCP MD5 signature as described in RFC 2385 |
| ttl (integer: 1..255 | default; Default: default) | Time To Leave, the hop limit for TCP connection. For example, if 'ttl=1' then only single
hop neighbors will be able to establish the connection. This property only affects EBGP peers.
|
| update-source (IP address | interface name;) | If address is specified, this address is used as the source address of the outgoing TCP connection. If interface name is specified, an address belonging to the interface is used as described. |
Read only status properties:
| Property | Description |
|---|---|
| remote-id (IP address) | BGP router ID of the remote end |
| local-address (IP address) | local address used for TCP connection |
| uptime (time) | how long the connection has been in established state |
| prefix-count (integer) | number routing prefixes received from this peer currently in routing table |
| updates-sent (integer) | total number of reachable routing prefixes advertised |
| updates-received (integer) | total number of reachable routing prefixes received |
| withdrawn-sent (integer) | total number of withdrawn routing prefixes advertised |
| withdrawn-received (integer) | total number of withdrawn routing prefixes received |
| remote-hold-time (time) | hold time value offered by the remote end |
| used-hold-time (time) | negotiated hold time value |
| used-keepalive-time (time) | negotiated keepalive message interval (used-hold-time / 3) |
| refresh-capability (yes | no) | |
| as4-capability (yes | no) | set to yes if peer supports 4-byte AS numbers |
| used-keepalive-time (time) | negotiated keepalive message interval (used-hold-time / 3) |
| state (idle | connect | active | opensent | openconfirm | established) | BGP protocol state |
Advertisements
Sub-menu: /routing bgp advertisements
Read only information about outgoing routing information currently advertised.
This information is calculated dynamically after 'print' command is issued. As a result, it may not correspond to the information that at the exact moment has been sent out. Especially if in case of slow connection, routing information prepared for output will spend long time in buffers. 'advertisements print' will show as things should be, not as they are!
| Property | Description |
|---|---|
| prefix (IP prefix) | the NLRI prefix sent out |
| nexthop (IP address) | the NEXT_HOP attribute value sent out |
| as-path (string) | the AS_PATH attribute value sent out |
| origin (igp | egp | incomplete) | the ORIGIN attribute value sent out |
| local-pref (integer) | the LOCAL_PREF attribute value sent out |
| med (integer) | the MULTI_EXIT_DISC attribute value sent out |
| atomic-aggregate (yes | no) | the ATOMIC_AGGREGATE attribute value sent out |
| aggregator (IP address) | the AGGREGATOR attribute value sent out |
| originator-id (IP address) | the ORIGINATOR_ID attribute value sent out |
| cluster-list (string) | the CLUSTER_LIST attribute value sent out |
| peer (string) | the peer this information is advertised to |
Network
Sub-menu: /routing bgp network
BGP network configuration. BGP Networks is a list of IP prefixes to be advertised.
| Property | Description |
|---|---|
| network (IP prefix;) | the aggregate prefix |
| synchronize (yes | no; Default: no) | install a route for this network only when there are some IGP routes falling under the range of this network |
Note: Since v3.28 synchronize option is removed. Matching IGP route in routing table is required, otherwise BGP network will not be advertised.
Aggregate
Sub-menu: /routing bgp aggregate
BGP allows the aggregation of specific routes into one route with. This menu ('/routing bgp aggregate') allows to specify which routes you want to aggregate, and what attributes to use for the route created by aggregation.
| Property | Description |
|---|---|
| advertise-filter (string;) | name of the filter chain used to select the routes from which to inherit attributes |
| attribute-filter (string;) | name of the filter chain used to set the attributes of the aggregate route |
| inherit-attributes (yes | no; Default: yes) | whether to inherit BGP attributes from aggregated routes |
| instance (string;) | the instance this network belongs to |
| prefix (IP prefix;) | the aggregate prefix |
| summary-only (yes | no; Default: yes) | whether to suppress advertisements of all routes that fall within the range of this aggregate |
| suppress-filter (string;) | name of the filter chain used to select the routes to be suppressed |
Read only status property:
| routes-used (integer) | aggregated route statistics.
|
Terminology
- aggregated routes - all routes, that fall within the range of this aggregate; they possibly are suppressed;
- aggregate route - route created by aggregation.
Notes
Each aggregate will only affect routes coming from peers that belong to it's instance.
'suppress-filter' is useful only if 'summary-only=no'; 'advertise-filter' is useful only if 'inherit-attributes=yes'
If result 'attribute-filter' match 'reject' or 'discard', the aggregate route is not created.
Vpnv4 route
Sub-menu: /routing bgp vpnv4-route
Read only information about vpnv4 routing information currently advertised.
| Property | Description |
|---|---|
| bgp-as-path (string;) | the AS_PATH attribute value |
| bgp-atomic-aggregate (string;) | the ATOMIC_AGGREGATE attribute value |
| bgp-communities (;) | |
| bgp-ext-communities (string;) | |
| bgp-local-pref (string;) | the LOCAL_PREF attribute value |
| bgp-med (string;) | the MULTI_EXIT_DISC attribute value |
| bgp-origin (igp|egp|incomplete;) | the ORIGIN attribute value |
| bgp-prepend (string;) | |
| bgp-weight (string;) | |
| dst-address (string;) | |
| gateway (string;) | |
| in-label (integer;) | assigned MPLS in label |
| interface (string;) | |
| out-label (integer;) | assigned MPLS out label |
| route-distinguisher (string;) |