--- /dev/null
+.. _ldp:
+
+***
+LDP
+***
+
+The *ldpd* daemon is a standardised protocol that permits exchanging MPLS label
+information between MPLS devices. The LDP protocol creates peering between
+devices, so as to exchange that label information. This information is stored in
+MPLS table of *zebra*, and it injects that MPLS information in the underlying
+system (Linux kernel or OpenBSD system for instance).
+*ldpd* provides necessary options to create a Layer 2 VPN across MPLS network.
+For instance, it is possible to interconnect several sites that share the same
+broadcast domain.
+
+FRR implements LDP as described in :rfc:`5036`; other LDP standard are the
+following ones: :rfc:`6720`, :rfc:`6667`, :rfc:`5919`, :rfc:`5561`, :rfc:`7552`,
+:rfc:`4447`.
+Because MPLS is already available, FRR also supports :rfc:`3031`.
+
+Running Ldpd
+============
+
+The *ldpd* daemon can be invoked with any of the common
+options (:ref:`common-invocation-options`).
+
+The *zebra* daemon must be running before *ldpd* is invoked.
+
+Configuration of *ldpd* is done in its configuration file
+:file:`ldpd.conf`.
+
+
+.. _understanding-ldp:
+
+Understanding LDP principles
+============================
+
+Let's first introduce some definitions that permit understand better the LDP
+protocol:
+
+- `LSR` : Labeled Switch Router. Networking devices handling labels used to
+ forward traffic between and through them.
+
+- `LER` : Labeled Edge Router. A Labeled edge router is located at the edge of
+ an MPLS network, generally between an IP network and an MPLS network.
+
+
+``LDP`` aims at sharing label information across devices. It tries to establish
+peering with remote LDP capable devices, first by discovering using UDP port 646
+, then by peering using TCP port 646. Once the TCP session is established, the
+label information is shared, through label advertisements.
+
+There are different methods to send label advertisement modes. The
+implementation actually supports the following : Liberal Label Retention +
+Downstream Unsolicited + Independent Control.
+The other advertising modes are depicted below, and compared with the current
+implementation.
+
+- Liberal label retention versus conservative mode
+ In liberal mode, every label sent by every LSR is stored in the MPLS table.
+ In conservative mode, only the label that was sent by the best next hop
+ (determined by the IGP metric) for that particular FEC is stored in the MPLS
+ table.
+
+- Independent LSP Control versus ordered LSP Control
+ MPLS has two ways of binding labels to FEC’s; either through ordered LSP
+ control, or independent LSP control.
+ Ordered LSP control only binds a label to a FEC if it is the egress LSR, or
+ the router received a label binding for a FEC from the next hop router. In
+ this mode, an MPLS router will create a label binding for each FEC and
+ distribute it to its neighbors so long as he has a entry in the RIB for the
+ destination.
+ In the other mode, label bindings are made without any dependencies on another
+ router advertising a label for a particular FEC. Each router makes it own
+ independent decision to create a label for each FEC.
+ By default IOS uses Independent LSP Control, while Juniper implements the
+ Ordered Control. Both modes are interoperable, the difference is that Ordered
+ Control prevent blackholing during the LDP convergence process, at cost of
+ slowing down the convergence itself
+
+- unsolicited downstream versus downstream on demand
+ Downstream on demand label distribution is where an LSR must explicitly
+ request that a label be sent from its downstream router for a particular FEC.
+ Unsolicited label distribution is where a label is sent from the downstream
+ router without the original router requesting it.
+
+.. _configuring-ldpd:
+
+.. _ldp-configuration:
+
+LDP Configuration
+===================
+
+.. index:: [no] mpls ldp
+.. clicmd:: [no] mpls ldp
+
+ Enable or disable LDP daemon
+
+.. index:: [no] router-id A.B.C.D
+.. clicmd:: [no] router-id A.B.C.D
+
+ The following command located under MPLS router node configures the MPLS
+ router-id of the local device.
+
+.. index:: [no] address-family [ipv4 | ipv6]
+.. clicmd:: [no] address-family [ipv4 | ipv6]
+
+ Configure LDP for IPv4 or IPv6 address-family. Located under MPLS route node,
+ this subnode permits configuring the LDP neighbors.
+
+.. index:: [no] interface IFACE
+.. clicmd:: [no] interface IFACE
+
+ Located under MPLS address-family node, use this command to enable or disable
+ LDP discovery per interface. IFACE stands for the interface name where LDP is
+ enabled. By default it is disabled. Once this command executed, the
+ address-family interface node is configured.
+
+.. index:: [no] discovery transport-address A.B.C.D | A:B::C:D
+.. clicmd:: [no] discovery transport-address A.B.C.D | A:B::C:D
+
+ Located under mpls address-family interface node, use this command to set
+ the IPv4 or IPv6 transport-address used by the LDP protocol to talk on this
+ interface.
+
+.. index:: [no] neighbor A.B.C.D password PASSWORD
+.. clicmd:: [no] neighbor A.B.C.D password PASSWORD
+
+ The following command located under MPLS router node configures the router
+ of a LDP device. This device, if found, will have to comply with the
+ configured password. PASSWORD is a clear text password wit its digest sent
+ through the network.
+
+.. index:: [no] neighbor A.B.C.D holdtime HOLDTIME
+.. clicmd:: [no] neighbor A.B.C.D holdtime HOLDTIME
+
+ The following command located under MPLS router node configures the holdtime
+ value in seconds of the LDP neighbor ID. Configuring it triggers a keepalive
+ mechanism. That value can be configured between 15 and 65535 seconds. After
+ this time of non response, the LDP established session will be considered as
+ set to down. By default, no holdtime is configured for the LDP devices.
+
+.. index:: [no] discovery hello holdtime HOLDTIME
+.. clicmd:: [no] discovery hello holdtime HOLDTIME
+
+.. index:: [no] discovery hello interval INTERVAL
+.. clicmd:: [no] discovery hello interval INTERVAL
+
+ INTERVAL value ranges from 1 to 65535 seconds. Default value is 5 seconds.
+ This is the value between each hello timer message sent.
+ HOLDTIME value ranges from 1 to 65535 seconds. Default value is 15 seconds.
+ That value is added as a TLV in the LDP messages.
+
+.. _show-ldp-information:
+
+Show LDP Information
+====================
+
+These commands dump various parts of *ldpd*.
+
+.. index:: show mpls ldp neighbor [A.B.C.D]
+.. clicmd:: show mpls ldp neighbor [A.B.C.D]
+
+ This command dumps the various neighbors discovered. Below example shows that
+ local machine has an operation neighbor with ID set to 1.1.1.1.
+
+ ::
+
+ west-vm# show mpls ldp neighbor
+ AF ID State Remote Address Uptime
+ ipv4 1.1.1.1 OPERATIONAL 1.1.1.1 00:01:37
+ west-vm#
+
+.. index:: show mpls ldp neighbor [A.B.C.D] capabilities
+.. clicmd:: show mpls ldp neighbor [A.B.C.D] capabilities
+
+.. index:: show mpls ldp neighbor [A.B.C.D] detail
+.. clicmd:: show mpls ldp neighbor [A.B.C.D] detail
+
+ Above commands dump other neighbor information.
+
+.. index:: show mpls ldp discovery [detail]
+.. clicmd:: show mpls ldp discovery [detail]
+
+.. index:: show mpls ldp ipv4 discovery [detail]
+.. clicmd:: show mpls ldp ipv4 discovery [detail]
+
+.. index:: show mpls ldp ipv6 discovery [detail]
+.. clicmd:: show mpls ldp ipv6 discovery [detail]
+
+ Above commands dump discovery information.
+
+.. index:: show mpls ldp ipv4 interface
+.. clicmd:: show mpls ldp ipv4 interface
+
+.. index:: show mpls ldp ipv6 interface
+.. clicmd:: show mpls ldp ipv6 interface
+
+ Above command dumps the IPv4 or IPv6 interface per where LDP is enabled.
+ Below output illustrates what is dumped for IPv4.
+
+ ::
+
+ west-vm# show mpls ldp ipv4 interface
+ AF Interface State Uptime Hello Timers ac
+ ipv4 eth1 ACTIVE 00:08:35 5/15 0
+ ipv4 eth3 ACTIVE 00:08:35 5/15 1
+
+
+.. index:: show mpls ldp ipv4|ipv6 binding
+.. clicmd:: show mpls ldp ipv4|ipv6 binding
+
+ Above command dumps the binding obtained through MPLS exchanges with LDP.
+
+ ::
+
+ west-vm# show mpls ldp ipv4 binding
+ AF Destination Nexthop Local Label Remote Label In Use
+ ipv4 1.1.1.1/32 1.1.1.1 16 imp-null yes
+ ipv4 2.2.2.2/32 1.1.1.1 imp-null 16 no
+ ipv4 10.0.2.0/24 1.1.1.1 imp-null imp-null no
+ ipv4 10.115.0.0/24 1.1.1.1 imp-null 17 no
+ ipv4 10.135.0.0/24 1.1.1.1 imp-null imp-null no
+ ipv4 10.200.0.0/24 1.1.1.1 17 imp-null yes
+ west-vm#
+
+LDP debugging commands
+========================
+
+.. index::
+ simple: debug mpls ldp KIND
+ simple: no debug mpls ldp KIND
+
+.. clicmd:: [no] debug mpls ldp KIND
+
+ Enable or disable debugging messages of a given kind. ``KIND`` can
+ be one of:
+
+ - ``discovery``
+ - ``errors``
+ - ``event``
+ - ``labels``
+ - ``messages``
+ - ``zebra``
+
+LDP Example Configuration
+=========================
+
+Below configuration gives a typical MPLS configuration of a device located in a
+MPLS backbone. LDP is enabled on two interfaces and will attempt to peer with
+two neighbors with router-id set to either 1.1.1.1 or 3.3.3.3.
+
+.. code-block:: frr
+
+ mpls ldp
+ router-id 2.2.2.2
+ neighbor 1.1.1.1 password test
+ neighbor 3.3.3.3 password test
+ !
+ address-family ipv4
+ discovery transport-address 2.2.2.2
+ !
+ interface eth1
+ !
+ interface eth3
+ !
+ exit-address-family
+ !
+
+
+Deploying LDP across a backbone generally is done in a full mesh configuration
+topology. LDP is typically deployed with an IGP like OSPF, that helps discover
+the remote IPs. Below example is an OSPF configuration extract that goes with
+LDP configuration
+
+.. code-block:: frr
+
+ router ospf
+ ospf router-id 2.2.2.2
+ network 0.0.0.0/0 area 0
+ !
+
+
+Below output shows the routing entry on the LER side. The OSPF routing entry
+(10.200.0.0) is associated with Label entry (17), and shows that MPLS push action
+that traffic to that destination will be applied.
+
+::
+
+ north-vm# show ip route
+ Codes: K - kernel route, C - connected, S - static, R - RIP,
+ O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
+ T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
+ F - PBR,
+ > - selected route, * - FIB route
+
+ O>* 1.1.1.1/32 [110/120] via 10.115.0.1, eth2, label 16, 00:00:15
+ O>* 2.2.2.2/32 [110/20] via 10.115.0.1, eth2, label implicit-null, 00:00:15
+ O 3.3.3.3/32 [110/10] via 0.0.0.0, loopback1 onlink, 00:01:19
+ C>* 3.3.3.3/32 is directly connected, loopback1, 00:01:29
+ O>* 10.0.2.0/24 [110/11] via 10.115.0.1, eth2, label implicit-null, 00:00:15
+ O 10.100.0.0/24 [110/10] is directly connected, eth1, 00:00:32
+ C>* 10.100.0.0/24 is directly connected, eth1, 00:00:32
+ O 10.115.0.0/24 [110/10] is directly connected, eth2, 00:00:25
+ C>* 10.115.0.0/24 is directly connected, eth2, 00:00:32
+ O>* 10.135.0.0/24 [110/110] via 10.115.0.1, eth2, label implicit-null, 00:00:15
+ O>* 10.200.0.0/24 [110/210] via 10.115.0.1, eth2, label 17, 00:00:15
+ north-vm#
+
projects / mirror_frr.git / commitdiff