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diff --git a/docs/routing/bgp.rst b/docs/routing/bgp.rst deleted file mode 100644 index c576d836..00000000 --- a/docs/routing/bgp.rst +++ /dev/null @@ -1,335 +0,0 @@ -.. _bgp: - -### -BGP -### - -:abbr:`BGP (Border Gateway Protocol)` is one of the Exterior Gateway Protocols -and the de facto standard interdomain routing protocol. The latest BGP version -is 4. BGP-4 is described in :rfc:`1771` and updated by :rfc:`4271`. :rfc:`2858` -adds multiprotocol support to BGP. - -VyOS makes use of :abbr:`FRR (Free Range Routing)` and we would like to thank -them for their effort! - -Basic Concepts -============== - -.. _bgp-autonomous-systems: - -Autonomous Systems ------------------- - -From :rfc:`1930`: - - An AS is a connected group of one or more IP prefixes run by one or more - network operators which has a SINGLE and CLEARLY DEFINED routing policy. - -Each AS has an identifying number associated with it called an :abbr:`ASN -(Autonomous System Number)`. This is a two octet value ranging in value from 1 -to 65535. The AS numbers 64512 through 65535 are defined as private AS numbers. -Private AS numbers must not be advertised on the global Internet. - -The :abbr:`ASN (Autonomous System Number)` is one of the essential elements of -BGP. BGP is a distance vector routing protocol, and the AS-Path framework -provides distance vector metric and loop detection to BGP. - -.. _bgp-address-families: - -Address Families ----------------- - -Multiprotocol extensions enable BGP to carry routing information for multiple -network layer protocols. BGP supports an Address Family Identifier (AFI) for -IPv4 and IPv6. - -.. _bgp-route-selection: - -Route Selection ---------------- - -The route selection process used by FRR's BGP implementation uses the following -decision criterion, starting at the top of the list and going towards the -bottom until one of the factors can be used. - -1. **Weight check** - - Prefer higher local weight routes to lower routes. - -2. **Local preference check** - - Prefer higher local preference routes to lower. - -3. **Local route check** - - Prefer local routes (statics, aggregates, redistributed) to received routes. - -4. **AS path length check** - - Prefer shortest hop-count AS_PATHs. - -5. **Origin check** - - Prefer the lowest origin type route. That is, prefer IGP origin routes to - EGP, to Incomplete routes. - -6. **MED check** - - Where routes with a MED were received from the same AS, prefer the route - with the lowest MED. - -7. **External check** - - Prefer the route received from an external, eBGP peer over routes received - from other types of peers. - -8. **IGP cost check** - - Prefer the route with the lower IGP cost. - -9. **Multi-path check** - - If multi-pathing is enabled, then check whether the routes not yet - distinguished in preference may be considered equal. If - :cfgcmd:`bgp bestpath as-path multipath-relax` is set, all such routes are - considered equal, otherwise routes received via iBGP with identical AS_PATHs - or routes received from eBGP neighbours in the same AS are considered equal. - -10. **Already-selected external check** - - Where both routes were received from eBGP peers, then prefer the route - which is already selected. Note that this check is not applied if - :cfgcmd:`bgp bestpath compare-routerid` is configured. This check can - prevent some cases of oscillation. - -11. **Router-ID check** - - Prefer the route with the lowest `router-ID`. If the route has an - `ORIGINATOR_ID` attribute, through iBGP reflection, then that router ID is - used, otherwise the `router-ID` of the peer the route was received from is - used. - -12. **Cluster-List length check** - - The route with the shortest cluster-list length is used. The cluster-list - reflects the iBGP reflection path the route has taken. - -13. **Peer address** - - Prefer the route received from the peer with the higher transport layer - address, as a last-resort tie-breaker. - -.. _bgp-capability-negotiation: - -Capability Negotiation ----------------------- - -When adding IPv6 routing information exchange feature to BGP. There were some -proposals. :abbr:`IETF (Internet Engineering Task Force)` -:abbr:`IDR (Inter Domain Routing)` adopted a proposal called Multiprotocol -Extension for BGP. The specification is described in :rfc:`2283`. The protocol -does not define new protocols. It defines new attributes to existing BGP. When -it is used exchanging IPv6 routing information it is called BGP-4+. When it is -used for exchanging multicast routing information it is called MBGP. - -*bgpd* supports Multiprotocol Extension for BGP. So if a remote peer supports -the protocol, *bgpd* can exchange IPv6 and/or multicast routing information. - -Traditional BGP did not have the feature to detect a remote peer's -capabilities, e.g. whether it can handle prefix types other than IPv4 unicast -routes. This was a big problem using Multiprotocol Extension for BGP in an -operational network. :rfc:`2842` adopted a feature called Capability -Negotiation. *bgpd* use this Capability Negotiation to detect the remote peer's -capabilities. If a peer is only configured as an IPv4 unicast neighbor, *bgpd* -does not send these Capability Negotiation packets (at least not unless other -optional BGP features require capability negotiation). - -By default, FRR will bring up peering with minimal common capability for the -both sides. For example, if the local router has unicast and multicast -capabilities and the remote router only has unicast capability the local router -will establish the connection with unicast only capability. When there are no -common capabilities, FRR sends Unsupported Capability error and then resets the -connection. - -.. _bgp-router-configuration: - -BGP Router Configuration -======================== - -ASN and Router ID ------------------ - -.. cfgcmd:: set protocols bgp <asn> - - First of all you must configure BGP router with the :abbr:`ASN (Autonomous - System Number)`. The AS number is an identifier for the autonomous system. - The BGP protocol uses the AS number for detecting whether the BGP connection - is internal or external. - -.. cfgcmd:: set protocols bgp <asn> parameters router-id - - This command specifies the router-ID. If router ID is not specified it will - use the highest interface IP address. - -Route Selection ---------------- - -.. cfgcmd:: set protocols bgp <asn> parameters bestpath as-path confed - - This command specifies that the length of confederation path sets and - sequences should be taken into account during the BGP best path - decision process. - -.. cfgcmd:: set protocols bgp <asn> parameters bestpath as-path multipath-relax - - This command specifies that BGP decision process should consider paths - of equal AS_PATH length candidates for multipath computation. Without - the knob, the entire AS_PATH must match for multipath computation. - -.. cfgcmd:: set protocols bgp <asn> parameters bestpath as-path ignore - - Ignore AS_PATH length when selecting a route - -IPv4 -^^^^ - -A simple eBGP configuration: - -**Node 1:** - -.. code-block:: none - - set protocols bgp 65534 neighbor 192.168.0.2 ebgp-multihop '2' - set protocols bgp 65534 neighbor 192.168.0.2 remote-as '65535' - set protocols bgp 65534 neighbor 192.168.0.2 update-source '192.168.0.1' - set protocols bgp 65534 address-family ipv4-unicast network '172.16.0.0/16' - set protocols bgp 65534 parameters router-id '192.168.0.1' - -**Node 2:** - -.. code-block:: none - - set protocols bgp 65535 neighbor 192.168.0.1 ebgp-multihop '2' - set protocols bgp 65535 neighbor 192.168.0.1 remote-as '65534' - set protocols bgp 65535 neighbor 192.168.0.1 update-source '192.168.0.2' - set protocols bgp 65535 address-family ipv4-unicast network '172.17.0.0/16' - set protocols bgp 65535 parameters router-id '192.168.0.2' - - -Don't forget, the CIDR declared in the network statement MUST **exist in your -routing table (dynamic or static), the best way to make sure that is true is -creating a static route:** - -**Node 1:** - -.. code-block:: none - - set protocols static route 172.16.0.0/16 blackhole distance '254' - -**Node 2:** - -.. code-block:: none - - set protocols static route 172.17.0.0/16 blackhole distance '254' - - -IPv6 -^^^^ - -A simple BGP configuration via IPv6. - -**Node 1:** - -.. code-block:: none - - set protocols bgp 65534 neighbor 2001:db8::2 ebgp-multihop '2' - set protocols bgp 65534 neighbor 2001:db8::2 remote-as '65535' - set protocols bgp 65534 neighbor 2001:db8::2 update-source '2001:db8::1' - set protocols bgp 65534 neighbor 2001:db8::2 address-family ipv6-unicast - set protocols bgp 65534 address-family ipv6-unicast network '2001:db8:1::/48' - set protocols bgp 65534 parameters router-id '10.1.1.1' - -**Node 2:** - -.. code-block:: none - - set protocols bgp 65535 neighbor 2001:db8::1 ebgp-multihop '2' - set protocols bgp 65535 neighbor 2001:db8::1 remote-as '65534' - set protocols bgp 65535 neighbor 2001:db8::1 update-source '2001:db8::2' - set protocols bgp 65535 neighbor 2001:db8::1 address-family ipv6-unicast - set protocols bgp 65535 address-family ipv6-unicast network '2001:db8:2::/48' - set protocols bgp 65535 parameters router-id '10.1.1.2' - -Don't forget, the CIDR declared in the network statement **MUST exist in your -routing table (dynamic or static), the best way to make sure that is true is -creating a static route:** - -**Node 1:** - -.. code-block:: none - - set protocols static route6 2001:db8:1::/48 blackhole distance '254' - -**Node 2:** - -.. code-block:: none - - set protocols static route6 2001:db8:2::/48 blackhole distance '254' - -Route Filter -^^^^^^^^^^^^ - -Route filter can be applied using a route-map: - -**Node1:** - -.. code-block:: none - - set policy prefix-list AS65535-IN rule 10 action 'permit' - set policy prefix-list AS65535-IN rule 10 prefix '172.16.0.0/16' - set policy prefix-list AS65535-OUT rule 10 action 'deny' - set policy prefix-list AS65535-OUT rule 10 prefix '172.16.0.0/16' - set policy prefix-list6 AS65535-IN rule 10 action 'permit' - set policy prefix-list6 AS65535-IN rule 10 prefix '2001:db8:2::/48' - set policy prefix-list6 AS65535-OUT rule 10 action 'deny' - set policy prefix-list6 AS65535-OUT rule 10 prefix '2001:db8:2::/48' - set policy route-map AS65535-IN rule 10 action 'permit' - set policy route-map AS65535-IN rule 10 match ip address prefix-list 'AS65535-IN' - set policy route-map AS65535-IN rule 10 match ipv6 address prefix-list 'AS65535-IN' - set policy route-map AS65535-IN rule 20 action 'deny' - set policy route-map AS65535-OUT rule 10 action 'deny' - set policy route-map AS65535-OUT rule 10 match ip address prefix-list 'AS65535-OUT' - set policy route-map AS65535-OUT rule 10 match ipv6 address prefix-list 'AS65535-OUT' - set policy route-map AS65535-OUT rule 20 action 'permit' - set protocols bgp 65534 neighbor 2001:db8::2 address-family ipv4-unicast route-map export 'AS65535-OUT' - set protocols bgp 65534 neighbor 2001:db8::2 address-family ipv4-unicast route-map import 'AS65535-IN' - set protocols bgp 65534 neighbor 2001:db8::2 address-family ipv6-unicast route-map export 'AS65535-OUT' - set protocols bgp 65534 neighbor 2001:db8::2 address-family ipv6-unicast route-map import 'AS65535-IN' - -**Node2:** - -.. code-block:: none - - set policy prefix-list AS65534-IN rule 10 action 'permit' - set policy prefix-list AS65534-IN rule 10 prefix '172.17.0.0/16' - set policy prefix-list AS65534-OUT rule 10 action 'deny' - set policy prefix-list AS65534-OUT rule 10 prefix '172.17.0.0/16' - set policy prefix-list6 AS65534-IN rule 10 action 'permit' - set policy prefix-list6 AS65534-IN rule 10 prefix '2001:db8:1::/48' - set policy prefix-list6 AS65534-OUT rule 10 action 'deny' - set policy prefix-list6 AS65534-OUT rule 10 prefix '2001:db8:1::/48' - set policy route-map AS65534-IN rule 10 action 'permit' - set policy route-map AS65534-IN rule 10 match ip address prefix-list 'AS65534-IN' - set policy route-map AS65534-IN rule 10 match ipv6 address prefix-list 'AS65534-IN' - set policy route-map AS65534-IN rule 20 action 'deny' - set policy route-map AS65534-OUT rule 10 action 'deny' - set policy route-map AS65534-OUT rule 10 match ip address prefix-list 'AS65534-OUT' - set policy route-map AS65534-OUT rule 10 match ipv6 address prefix-list 'AS65534-OUT' - set policy route-map AS65534-OUT rule 20 action 'permit' - set protocols bgp 65535 neighbor 2001:db8::1 address-family ipv4-unicast route-map export 'AS65534-OUT' - set protocols bgp 65535 neighbor 2001:db8::1 address-family ipv4-unicast route-map import 'AS65534-IN' - set protocols bgp 65535 neighbor 2001:db8::1 address-family ipv6-unicast route-map export 'AS65534-OUT' - set protocols bgp 65535 neighbor 2001:db8::1 address-family ipv6-unicast route-map import 'AS65534-IN' - -We could expand on this and also deny link local and multicast in the rule 20 -action deny. |