docs/user-guide/bgpcep-guide/bgp/bgp-user-guide-additional-path-capability.rst

   1 .. _bgp-user-guide-additional-path-capability:
   2
   3 Additional Path Capability
   4 ==========================
   5 The ADD-PATH capability allows to advertise multiple paths for the same address prefix.
   6 It can help with optimal routing and routing convergence in a network by providing potential alternate or backup paths.
   7
   8 .. contents:: Contents
   9    :depth: 2
  10    :local:
  11
  12 Configuration
  13 ^^^^^^^^^^^^^
  14 This section shows a way to enable ADD-PATH capability in BGP speaker and peer configuration.
  15
  16 .. note:: The capability is applicable for IP Unicast, IP Labeled Unicast and Flow Specification address families.
  17
  18 BGP Speaker
  19 '''''''''''
  20 To enable ADD-PATH capability in BGP plugin, first configure BGP speaker instance:
  21
  22 **URL:** ``/restconf/config/openconfig-network-instance:network-instances/network-instance/global-bgp/openconfig-network-instance:protocols``
  23
  24 **Method:** ``POST``
  25
  26 **Content-Type:** ``application/xml``
  27
  28 **Request Body:**
  29
  30 .. code-block:: xml
  31    :linenos:
  32    :emphasize-lines: 14
  33
  34    <protocol xmlns="http://openconfig.net/yang/network-instance">
  35        <name>bgp-example</name>
  36        <identifier xmlns:x="http://openconfig.net/yang/policy-types">x:BGP</identifier>
  37        <bgp xmlns="urn:opendaylight:params:xml:ns:yang:bgp:openconfig-extensions">
  38            <global>
  39                <config>
  40                    <router-id>192.0.2.2</router-id>
  41                    <as>65000</as>
  42                </config>
  43                <afi-safis>
  44                    <afi-safi>
  45                        <afi-safi-name xmlns:x="http://openconfig.net/yang/bgp-types">x:IPV4-UNICAST</afi-safi-name>
  46                        <receive>true</receive>
  47                        <send-max>2</send-max>
  48                    </afi-safi>
  49                </afi-safis>
  50            </global>
  51        </bgp>
  52    </protocol>
  53
  54 @line 14: Defines path selection strategy: *send-max* > 1 -> Advertise N Paths or *send-max* = 0 -> Advertise All Paths
  55
  56 Here is an example for update a specific family with enable ADD-PATH capability
  57
  58 **URL:** ``/restconf/config/openconfig-network-instance:network-instances/network-instance/global-bgp/openconfig-network-instance:protocols/protocol/openconfig-policy-types:BGP/bgp-example/bgp/global/afi-safis/afi-safi/openconfig-bgp-types:IPV4%2DUNICAST``
  59
  60 **Method:** ``PUT``
  61
  62 **Content-Type:** ``application/xml``
  63
  64 **Request Body:**
  65
  66 .. code-block:: xml
  67
  68    <afi-safi xmlns="urn:opendaylight:params:xml:ns:yang:bgp:openconfig-extensions">
  69       <afi-safi-name xmlns:x="http://openconfig.net/yang/bgp-types">x:IPV4-UNICAST</afi-safi-name>
  70       <receive>true</receive>
  71       <send-max>0</send-max>
  72    </afi-safi>
  73
  74 BGP Peer
  75 ''''''''
  76 Here is an example for BGP peer configuration with enabled ADD-PATH capability.
  77
  78 **URL:** ``/restconf/config/openconfig-network-instance:network-instances/network-instance/global-bgp/openconfig-network-instance:protocols/protocol/openconfig-policy-types:BGP/bgp-example/bgp/neighbors``
  79
  80 **Method:** ``POST``
  81
  82 **Content-Type:** ``application/xml``
  83
  84 **Request Body:**
  85
  86 .. code-block:: xml
  87
  88    <neighbor xmlns="urn:opendaylight:params:xml:ns:yang:bgp:openconfig-extensions">
  89        <neighbor-address>192.0.2.1</neighbor-address>
  90        <afi-safis>
  91            <afi-safi>
  92                <afi-safi-name xmlns:x="http://openconfig.net/yang/bgp-types">x:IPV4-LABELLED-UNICAST</afi-safi-name>
  93            </afi-safi>
  94            <afi-safi>
  95                <afi-safi-name xmlns:x="http://openconfig.net/yang/bgp-types">x:IPV4-UNICAST</afi-safi-name>
  96                <receive>true</receive>
  97                <send-max>0</send-max>
  98            </afi-safi>
  99        </afi-safis>
 100    </neighbor>
 101
 102 .. note:: The path selection strategy is not configurable on per peer basis. The send-max presence indicates a willingness to send ADD-PATH NLRIs to the neighbor.
 103
 104 Here is an example for update specific family BGP peer configuration with enabled ADD-PATH capability.
 105
 106 **URL:** ``/restconf/config/openconfig-network-instance:network-instances/network-instance/global-bgp/openconfig-network-instance:protocols/protocol/openconfig-policy-types:BGP/bgp-example/bgp/neighbors/neighbor/192.0.2.1/afi-safis/afi-safi/openconfig-bgp-types:IPV4%2DUNICAST``
 107
 108 **Method:** ``PUT``
 109
 110 **Content-Type:** ``application/xml``
 111
 112 **Request Body:**
 113
 114 .. code-block:: xml
 115
 116    <afi-safi xmlns="urn:opendaylight:params:xml:ns:yang:bgp:openconfig-extensions">
 117       <afi-safi-name xmlns:x="http://openconfig.net/yang/bgp-types">x:IPV4-UNICAST</afi-safi-name>
 118       <receive>true</receive>
 119       <send-max>0</send-max>
 120    </afi-safi>
 121
 122 Usage
 123 ^^^^^
 124 The IPv4 Unicast table with enabled ADD-PATH capability in an instance of the speaker's Loc-RIB can be verified via REST:
 125
 126 **URL:** ``/restconf/operational/bgp-rib:bgp-rib/rib/bgp-example/loc-rib/tables/bgp-types:ipv4-address-family/bgp-types:unicast-subsequent-address-family/ipv4-routes``
 127
 128 **Method:** ``GET``
 129
 130 **Response Body:**
 131
 132 .. code-block:: xml
 133    :linenos:
 134    :emphasize-lines: 3
 135
 136    <ipv4-routes xmlns="urn:opendaylight:params:xml:ns:yang:bgp-inet">
 137        <ipv4-route>
 138            <path-id>1</path-id>
 139            <prefix>193.0.2.1/32</prefix>
 140            <attributes>
 141                <as-path></as-path>
 142                <origin>
 143                    <value>igp</value>
 144                </origin>
 145                <local-pref>
 146                    <pref>100</pref>
 147                </local-pref>
 148                <ipv4-next-hop>
 149                    <global>10.0.0.1</global>
 150                </ipv4-next-hop>
 151            </attributes>
 152        </ipv4-route>
 153        <ipv4-route>
 154            <path-id>2</path-id>
 155            <prefix>193.0.2.1/32</prefix>
 156            <attributes>
 157                <as-path></as-path>
 158                <origin>
 159                    <value>igp</value>
 160                </origin>
 161                <local-pref>
 162                    <pref>100</pref>
 163                </local-pref>
 164                <ipv4-next-hop>
 165                    <global>10.0.0.2</global>
 166                </ipv4-next-hop>
 167            </attributes>
 168        </ipv4-route>
 169    </ipv4-routes>
 170
 171 @line 3: The routes with the same destination are distinguished by *path-id* attribute.
 172
 173 References
 174 ^^^^^^^^^^
 175 * `Advertisement of Multiple Paths in BGP <https://tools.ietf.org/html/rfc7911>`_
 176 * `Best Practices for Advertisement of Multiple Paths in IBGP <https://tools.ietf.org/html/draft-ietf-idr-add-paths-guidelines-08>`_