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diff --git a/docs/configuration/protocols/mpls.md b/docs/configuration/protocols/mpls.md new file mode 100644 index 00000000..71b14be2 --- /dev/null +++ b/docs/configuration/protocols/mpls.md @@ -0,0 +1,285 @@ +(mpls)= + +# MPLS + +{abbr}`MPLS (Multi-Protocol Label Switching)` is a packet forwarding paradigm +which differs from regular IP forwarding. Instead of IP addresses being used to +make the decision on finding the exit interface, a router will instead use an +exact match on a 32 bit/4 byte header called the MPLS label. This label is +inserted between the ethernet (layer 2) header and the IP (layer 3) header. +One can statically or dynamically assign label allocations, but we will focus +on dynamic allocation of labels using some sort of label distribution protocol +(such as the aptly named Label Distribution Protocol / LDP, Resource Reservation +Protocol / RSVP, or Segment Routing through OSPF/ISIS). These protocols allow +for the creation of a unidirectional/unicast path called a labeled switched +path (initialized as LSP) throughout the network that operates very much like +a tunnel through the network. An easy way of thinking about how an MPLS LSP +actually forwards traffic throughout a network is to think of a GRE tunnel. +They are not the same in how they operate, but they are the same in how they +handle the tunneled packet. It would be good to think of MPLS as a tunneling +technology that can be used to transport many different types of packets, to +aid in traffic engineering by allowing one to specify paths throughout the +network (using RSVP or SR), and to generally allow for easier intra/inter +network transport of data packets. + +For more information on how MPLS label switching works, please go visit +[Wikipedia (MPLS)]. + +:::{note} +MPLS support in VyOS is not finished yet, and therefore its +functionality is limited. Currently there is no support for MPLS enabled VPN +services such as L2VPNs and mVPNs. RSVP support is also not present as the +underlying routing stack (FRR) does not implement it. Currently VyOS +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). +::: + +## Label Distribution Protocol + +The {abbr}`MPLS (Multi-Protocol Label Switching)` architecture does not assume +a single protocol to create MPLS paths. VyOS supports the Label Distribution +Protocol (LDP) as implemented by FRR, based on {rfc}`5036`. + +{abbr}`LDP (Label Distribution Protocol)` is a TCP based MPLS signaling protocol +that distributes labels creating MPLS label switched paths in a dynamic manner. +LDP is not a routing protocol, as it relies on other routing protocols for +forwarding decisions. LDP cannot bootstrap itself, and therefore relies on said +routing protocols for communication with other routers that use LDP. + +In order to allow for LDP on the local router to exchange label advertisements +with other routers, a TCP session will be established between automatically +discovered and statically assigned routers. LDP will try to establish a TCP +session to the **transport address** of other routers. Therefore for LDP to +function properly please make sure the transport address is shown in the +routing table and reachable to traffic at all times. + +It is highly recommended to use the same address for both the LDP router-id and +the discovery transport address, but for VyOS MPLS LDP to work both parameters +must be explicitly set in the configuration. + +Another thing to keep in mind with LDP is that much like BGP, it is a protocol +that runs on top of TCP. It however does not have an ability to do something +like a refresh capability like BGPs route refresh capability. Therefore one +might have to reset the neighbor for a capability change or a configuration +change to work. + +## Configuration Options + +```{cfgcmd} set protocols mpls interface \<interface\> + +Use this command to enable MPLS processing on the interface you define. +``` + + +```{cfgcmd} set protocols mpls ldp interface \<interface\> + +Use this command to enable LDP on the interface you define. +``` + + +```{cfgcmd} set protocols mpls ldp router-id \<address\> + +Use this command to configure the IP address used as the LDP router-id of the +local device. +``` + + +```{cfgcmd} set protocols mpls ldp discovery transport-ipv4-address \<address\> + +``` +```{cfgcmd} set protocols mpls ldp discovery transport-ipv6-address \<address\> + +Use this command to set the IPv4 or IPv6 transport-address used by LDP. +``` + +```{cfgcmd} set protocols mpls ldp neighbor \<address\> password \<password\> + +Use this command to configure authentication for LDP peers. Set the +IP address of the LDP peer and a password that should be shared in +order to become neighbors. +``` + +```{cfgcmd} set protocols mpls ldp neighbor \<address\> session-holdtime \<seconds\> + +Use this command to configure a specific session hold time for LDP peers. +Set the IP address of the LDP peer and a session hold time that should be +configured for it. You may have to reset the neighbor for this to work. +``` + +```{cfgcmd} set protocols mpls ldp neighbor \<address\> ttl-security \<disable | hop count\> + +Use this command to enable, disable, or specify hop count for TTL security +for LDP peers. By default the value is set to 255 (or max TTL). +``` + +```{eval-rst} +.. cfgcmd:: set protocols mpls ldp discovery hello-ipv4-interval <seconds> +.. cfgcmd:: set protocols mpls ldp discovery hello-ipv4-holdtime <seconds> +.. cfgcmd:: set protocols mpls ldp discovery hello-ipv6-interval <seconds> +.. cfgcmd:: set protocols mpls ldp discovery hello-ipv6-holdtime <seconds> + + Use these commands if you would like to set the discovery hello and hold time + parameters. +``` + +```{eval-rst} +.. cfgcmd:: set protocols mpls ldp discovery session-ipv4-holdtime <seconds> +.. cfgcmd:: set protocols mpls ldp discovery session-ipv6-holdtime <seconds> + + Use this command if you would like to set the TCP session hold time intervals. +``` + +```{eval-rst} +.. cfgcmd:: set protocols mpls ldp import ipv4 import-filter filter-access-list + <access list number> +.. cfgcmd:: set protocols mpls ldp import ipv6 import-filter filter-access-list6 + <access list number> + + Use these commands to control the importing of forwarding equivalence classes + (FECs) for LDP from neighbors. This would be useful for example on only + accepting the labeled routes that are needed and not ones that are not + needed, such as accepting loopback interfaces and rejecting all others. +``` + +```{eval-rst} +.. cfgcmd:: set protocols mpls ldp export ipv4 export-filter filter-access-list + <access list number> +.. cfgcmd:: set protocols mpls ldp export ipv6 export-filter filter-access-list6 + <access list number> + + Use these commands to control the exporting of forwarding equivalence classes + (FECs) for LDP to neighbors. This would be useful for example on only + announcing the labeled routes that are needed and not ones that are not + needed, such as announcing loopback interfaces and no others. +``` + +```{eval-rst} +.. cfgcmd:: set protocols mpls ldp export ipv4 explicit-null +.. cfgcmd:: set protocols mpls ldp export ipv6 explicit-null + + Use this command if you would like for the router to advertise FECs with a + label of 0 for explicit null operations. +``` + +```{eval-rst} +.. cfgcmd:: set protocols mpls ldp allocation ipv4 access-list <access list number> +.. cfgcmd:: set protocols mpls ldp allocation ipv6 access-list6 <access list number> + + Use this command if you would like to control the local FEC allocations for + LDP. A good example would be for your local router to not allocate a label for + everything. Just a label for what it's useful. A good example would be just a + loopback label. +``` + +```{cfgcmd} set protocols mpls ldp parameters cisco-interop-tlv + +Use this command to use a Cisco non-compliant format to send and interpret +the Dual-Stack capability TLV for IPv6 LDP communications. This is related to +{rfc}`7552`. +``` + +```{cfgcmd} set protocols mpls ldp parameters ordered-control + +Use this command to use ordered label distribution control mode. FRR +by default uses independent label distribution control mode for label +distribution. This is related to {rfc}`5036`. +``` + +```{cfgcmd} set protocols mpls ldp parameters transport-prefer-ipv4 + +Use this command to prefer IPv4 for TCP peer transport connection for LDP +when both an IPv4 and IPv6 LDP address are configured on the same interface. +``` + +```{cfgcmd} set protocols mpls ldp targeted-neighbor ipv4 enable +``` + +```{cfgcmd} set protocols mpls ldp targeted-neighbor ipv6 enable + +Use this command to enable targeted LDP sessions to the local router. The +router will then respond to any sessions that are trying to connect to it that +are not a link local type of TCP connection. +``` + +```{cfgcmd} set protocols mpls ldp targeted-neighbor ipv4 address \<address\> +``` + +```{cfgcmd} set protocols mpls ldp targeted-neighbor ipv6 address \<address\> + +Use this command to enable the local router to try and connect with a targeted +LDP session to another router. +``` + +```{cfgcmd} set protocols mpls ldp targeted-neighbor ipv4 hello-holdtime \<seconds\> +``` + +```{cfgcmd} set protocols mpls ldp targeted-neighbor ipv4 hello-interval \<seconds\> +``` + +```{cfgcmd} set protocols mpls ldp targeted-neighbor ipv6 hello-holdtime \<seconds\> +``` + +```{cfgcmd} set protocols mpls ldp targeted-neighbor ipv6 hello-interval \<seconds\> + +Use these commands if you would like to set the discovery hello and hold time +parameters for the targeted LDP neighbors. +``` + +### Sample configuration to setup LDP on VyOS + +```none +set protocols ospf area 0 network '192.168.255.252/32' <--- Routing for loopback +set protocols ospf area 0 network '192.168.0.5/32' <--- Routing for an interface connecting to the network +set protocols ospf parameters router-id '192.168.255.252' <--- Router ID setting for OSPF +set protocols mpls interface 'eth1' <--- Enable MPLS for an interface connecting to network +set protocols mpls ldp discovery transport-ipv4-address '192.168.255.252' <--- Transport address for LDP for TCP sessions to connect to +set protocols mpls ldp interface 'eth1' <--- Enable LDP for an interface connecting to network +set protocols mpls ldp interface 'lo' <--- Enable LDP on loopback for future services connectivity +set protocols mpls ldp router-id '192.168.255.252' <--- Router ID setting for LDP +set interfaces ethernet eth1 address '192.168.0.5/31' <--- Interface IP for connecting to network +set interfaces loopback lo address '192.168.255.252/32' <--- Interface loopback IP for router ID and other uses +``` + +## Operational Mode Commands + +When LDP is working, you will be able to see label information in the outcome +of `show ip route`. Besides that information, there are also specific *show* +commands for LDP: + +### Show + +```{opcmd} show mpls ldp binding + +Use this command to see the Label Information Base. + +``` + +```{opcmd} show mpls ldp discovery + +Use this command to see discovery hello information +``` + +```{opcmd} show mpls ldp interface + +Use this command to see LDP interface information +``` + +```{opcmd} show mpls ldp neighbor + +Use this command to see LDP neighbor information +``` + +```{opcmd} show mpls ldp neighbor detail + +Use this command to see detailed LDP neighbor information +``` + +### Reset + +```{opcmd} reset mpls ldp neighbor \<IPv4 or IPv6 address\> + +Use this command to reset an LDP neighbor/TCP session that is established +``` + +[wikipedia (mpls)]: <https://en.wikipedia.org/wiki/Multiprotocol_Label_Switching> |