diff options
Diffstat (limited to 'doc/user/ldpd.rst')
| -rw-r--r-- | doc/user/ldpd.rst | 379 |
1 files changed, 379 insertions, 0 deletions
diff --git a/doc/user/ldpd.rst b/doc/user/ldpd.rst new file mode 100644 index 0000000..682443a --- /dev/null +++ b/doc/user/ldpd.rst @@ -0,0 +1,379 @@ +.. _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`). + +.. option:: --ctl_socket + + This option allows you to override the path to the ldpd.sock file + used to control this daemon. If specified this option overrides + the -N option path addition. + +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 +=================== + +.. clicmd:: mpls ldp + + Enable or disable LDP daemon + +.. clicmd:: router-id A.B.C.D + + The following command located under MPLS router node configures the MPLS + router-id of the local device. + +.. clicmd:: ordered-control + + Configure LDP Ordered Label Distribution Control. + +.. clicmd:: address-family [ipv4 | ipv6] + + Configure LDP for IPv4 or IPv6 address-family. Located under MPLS route node, + this subnode permits configuring the LDP neighbors. + +.. clicmd:: 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. + +.. clicmd:: 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. + +.. clicmd:: ttl-security disable + + Located under the LDP address-family node, use this command to disable the + GTSM procedures described in RFC 6720 (for the IPv4 address-family) and + RFC 7552 (for the IPv6 address-family). + + Since GTSM is mandatory for LDPv6, the only effect of disabling GTSM for the + IPv6 address-family is that *ldpd* will not discard packets with a hop limit + below 255. This may be necessary to interoperate with older implementations. + Outgoing packets will still be sent using a hop limit of 255 for maximum + compatibility. + + If GTSM is enabled, multi-hop neighbors should have either GTSM disabled + individually or configured with an appropriate ttl-security hops distance. + +.. clicmd:: 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. + +.. clicmd:: 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. + +.. clicmd:: neighbor A.B.C.D ttl-security disable + + Located under the MPLS LDP node, use this command to override the global + configuration and enable/disable GTSM for the specified neighbor. + +.. clicmd:: neighbor A.B.C.D ttl-security hops (1-254) + + Located under the MPLS LDP node, use this command to set the maximum number + of hops the specified neighbor may be away. When GTSM is enabled for this + neighbor, incoming packets are required to have a TTL/hop limit of 256 + minus this value, ensuring they have not passed through more than the + expected number of hops. The default value is 1. + +.. clicmd:: discovery hello holdtime HOLDTIME + +.. clicmd:: 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. + +.. clicmd:: dual-stack transport-connection prefer ipv4 + + When *ldpd* is configured for dual-stack operation, the transport connection + preference is IPv6 by default (as specified by :rfc:`7552`). On such + circumstances, *ldpd* will refuse to establish TCP connections over IPv4. + You can use above command to change the transport connection preference to + IPv4. In this case, it will be possible to distribute label mappings for + IPv6 FECs over TCPv4 connections. + +.. _show-ldp-information: + +Show LDP Information +==================== + +These commands dump various parts of *ldpd*. + +.. 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# + +.. clicmd:: show mpls ldp neighbor [A.B.C.D] capabilities + +.. clicmd:: show mpls ldp neighbor [A.B.C.D] detail + + Above commands dump other neighbor information. + +.. clicmd:: show mpls ldp discovery [detail] + +.. clicmd:: show mpls ldp ipv4 discovery [detail] + +.. clicmd:: show mpls ldp ipv6 discovery [detail] + + Above commands dump discovery information. + +.. clicmd:: show mpls ldp ipv4 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 + + +.. 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 +======================== + + +.. clicmd:: debug mpls ldp KIND + + Enable or disable debugging messages of a given kind. ``KIND`` can + be one of: + + - ``discovery`` + - ``errors`` + - ``event`` + - ``labels`` + - ``messages`` + - ``zebra`` + + +Sample 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# + + +Additional example demonstrating use of some miscellaneous config options: + +.. code-block:: frr + + interface eth0 + ! + interface eth1 + ! + interface lo + ! + mpls ldp + dual-stack cisco-interop + neighbor 10.0.1.5 password opensourcerouting + neighbor 172.16.0.1 password opensourcerouting + ! + address-family ipv4 + discovery transport-address 10.0.1.1 + label local advertise explicit-null + ! + interface eth0 + ! + interface eth1 + ! + ! + address-family ipv6 + discovery transport-address 2001:db8::1 + ! + interface eth1 + ! + ! + ! + l2vpn ENG type vpls + bridge br0 + member interface eth2 + ! + member pseudowire mpw0 + neighbor lsr-id 1.1.1.1 + pw-id 100 + ! + ! + |