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diff --git a/docs/gettingstarted/developers/fib20/mplsfib.rst b/docs/gettingstarted/developers/fib20/mplsfib.rst index 5fee7d0cd7f..c9f3d5d9ad1 100644 --- a/docs/gettingstarted/developers/fib20/mplsfib.rst +++ b/docs/gettingstarted/developers/fib20/mplsfib.rst @@ -1,45 +1,87 @@ .. _mplsfib: MPLS FIB ----------- +-------- -There is a tight coupling between IP and MPLS forwarding. MPLS forwarding -equivalence classes (FECs) are often an IP prefix Рthat is to say that traffic -matching a given IP prefix is routed into a MPLS label switch path (LSP). It is -thus necessary to be able to associated a given prefix/route with an [out-going] -MPLS label that will be imposed when the packet is forwarded. This is configured -as: +Implementation +^^^^^^^^^^^^^^^ + +The MPLS FIB is implemented using exactly the same data structures as +the IP FIB. The only difference is the implementation of the +table. Whereas for IPv4 this is an mtrie and for IPv6 a hash table, +for MPLS it is a flat array indexed by a 21 bit key (label & EOS +bit). This implementation is chosen to favour packet forwarding speed. + +Basics +^^^^^^ + +MPLS is not enabled by default. There are two steps to get +started. First, create the default MPLS FIB: .. code-block:: console - $ ip route add 1.1.1.1/32 via 10.10.10.10 GigabitEthernet0/8/0 out-label 33 + $ mpls table add 0 + +With '0' being the magic number for the 'default' table (just like it +is for IPv[46]). One can create other MPLS tables, but, unlike IP +tables, one cannot 'bind' non-default MPLS tables to interfaces, in +other words all MPLS packets received on an interface will always +result in a lookup in the default table. One has to be more inventive +to use the non-default tables... -packets matching 1.1.1.1/32 will be forwarded out GigabitEthernet0/8/0 and have MPLS label -33 imposed. More than one out-going label can be specified. Out-going MPLS labels -can be applied to recursive and non-recursive routes, e.g; +Secondly, for *each* interface on which you wish to *receive* MPLS +packets, that interface must be MPLS 'enabled' .. code-block:: console - $ ip route add 2.2.2.0/24 via 1.1.1.1 out-label 34 + $ set interface mpls GigEthernet0/0/0 enable -packets matching 2.2.2.0/24 will thus have two MPLS labels imposed; 34 and 33. -This is the realisation of, e,g, an MPLS BGP VPNv4. +there is no equivalent enable for transmit, all that is required is to +use an interface as an egress path. -To associate/allocate a local-label for a prefix, and thus have packets to that -local-label forwarded equivalently to the prefix do; +Entries in the MPLS FIB can be displayed with: .. code-block:: console - $ mpls local-label 99 2.2.2.0/24 + $ sh mpls fib [table X] [label] + +There is a tight coupling between IP and MPLS forwarding. MPLS +forwarding equivalence classes (FECs) are often an IP prefix – that is +to say that traffic matching a given IP prefix is routed into a MPLS +label switch path (LSP). It is thus necessary to be able to associated +a given prefix/route with an [out-going] MPLS label that will be +imposed when the packet is forwarded. This is configured as: + +.. code-block:: console + + $ ip route add 1.1.1.1/32 via 10.10.10.10 GigEthernet0/0/0 out-labels 33 + +packets matching 1.1.1.1/32 will be forwarded out GigEthernet0/0/0 and have +MPLS label 33 imposed. More than one out-going label can be +specified. Out-going MPLS labels can be applied to recursive and +non-recursive routes, e.g; + +.. code-block:: console -In the API this action is called a *bind*. + $ ip route add 2.2.2.0/24 via 1.1.1.1 out-labels 34 -The router receiving the MPLS encapsulated packets needs to be programmed with -actions associated which each label value Рthis is the role of the MPLS FIB. -The MPLS FIB Is a table, whose key is the MPLS label value and end-of-stack (EOS) -bit, which stores the action to perform on packets with matching encapsulation. +packets matching 2.2.2.0/24 will thus have two MPLS labels imposed; 34 +and 33. This is the realisation of, e,g, an MPLS BGP VPNv4. -Currently supported actions are: +To associate/allocate a local-label for a prefix, and thus have +packets to that local-label forwarded equivalently to the prefix do; + +.. code-block:: console + + $ mpls local-label 99 2.2.2.0/24 + +In the API this action is called a ‘bind’. +The router receiving the MPLS encapsulated packets needs to be +programmed with actions associated which each label value – this is +the role of the MPLS FIB. The MPLS FIB Is a table, whose key is the +MPLS label value and end-of-stack (EOS) bit, which stores the action +to perform on packets with matching encapsulation. Currently supported +actions are: #. Pop the label and perform an IPv[46] lookup in a specified table #. Pop the label and forward via a specified next-hop (this is penultimate-hop-pop, PHP) @@ -47,44 +89,105 @@ Currently supported actions are: These can be programmed respectively by: -#. mpls local-label 33 ip4-lookup-in-table X -#. mpls local-label 33 via 10.10.10.10 GigabitEthernet0/8/0 -#. mpls local-label 33 via 10.10.10.10 GigabitEthernet0/8/0 out-label 66 +#. mpls local-label 33 eos ip4-lookup-in-table X +#. mpls local-label 33 [eos] via 10.10.10.10 GigEthernet0/0/0 +#. mpls local-label 33 [eos] via 10.10.10.10 GigEthernet0/0/0 out-labels 66 -the latter is an example of an MPLS cross connect. Any description of a next-hop, -recursive, non-recursive, labelled, non-labelled, etc, that is valid for an IP -prefix, is also valid for an MPLS local-label. +the latter is an example of an MPLS cross connect. Any description of +a next-hop, recursive, non-recursive, labelled, non-labelled, etc, +that is valid for an IP prefix, is also valid for an MPLS +local-label. Note the use of the 'eos' keyword which indicates the +programming is for the case when the label is end-of-stack. The last +two operations can apply to both eos and non-eos packets, but the pop +and IP lookup only to an eos packet. -Implementation -^^^^^^^^^^^^^^^ -The MPLS FIB is implemented using exactly the same data structures as the IP FIB. -The only difference is the implementation of the table. Whereas for IPv4 this is -an mtrie and for IPv6 a hash table, for MPLS it is a flat array indexed by a 21 -bit key (label & EOS bit). This implementation is chosen to favour packet -forwarding speed. +MPLS VPN +^^^^^^^^ + +To configure an MPLS VPN for a PE the follow example can be used. + +Step 1; Configure routes to the iBGP peers - note these route MUST +have out-going labels; + +.. code-block:: console + + $ ip route add 10.0.0.1/32 via 192.168.1.2 Eth0 out-labels 33 + $ ip route add 10.0.0.2/32 via 192.168.2.2 Eth0 out-labels 34 + +Step 2; Configure the customer 'VRF' + +.. code-block:: console + + $ ip table add 2 + +Step 3; add a route via the iBGP peer[s] with the MPLS label +advertised by that peer + +.. code-block:: console + + $ ip route add table 2 10.10.10.0/24 via 10.0.0.2 next-hop-table 0 out-label 122 + $ ip route add table 2 10.10.10.0/24 via 10.0.0.1 next-hop-table 0 out-label 121 + +Step 4; add a route via the eBGP peer + +.. code-block:: console + + $ ip route add table 2 10.10.20.0/24 via 172.16.0.1 next-hop-table 2 + +Step 5; depending on the label allocation scheme used, add routes to +the MPLS FIB to accept incoming labelled packets: + +#. per-prefix label scheme - this command 'binds' the label to the same + forwarding as the IP route + + .. code-block:: console + + $ mpls local-label 99 10.10.20.0/24 + +#. per-CE label scheme - this pops the incoming label and forwards via + the next-hop provided. Append config for 'out-labels' if so desired. + + .. code-block:: console + + $ mpls local-label 99 via 172.16.0.1 next-hop-table 2 + +#. per-VRF label scheme + + .. code-block:: console + + $ mpls local-label 99 via ip4-lookup-in-table 2 MPLS Tunnels -^^^^^^^^^^^^^ +^^^^^^^^^^^^ -VPP no longer supports MPLS tunnels that are coupled to a particular transport, +MPLS tunnels are unidirectional and can impose a stack of labels. They +are 'normal' interfaces and thus can be used, for example, as the +target for IP routes and L2 cross-connects. To construct a tunnel: -i.e. MPLSoGRE or MPLSoEth. Such tight coupling is not beneficial. Instead VPP supports; +.. code-block:: console -#. MPLS LSPs associated with IP prefixes and MPLS local-labels (as described above) which are transport independent (i.e. the IP route could be reachable over a GRE tunnel, or any other interface type). -#. A generic uni-directional MPLS tunnel interface that is transport independent. + $ mpls tunnel add via 10.10.10.10 GigEthernet0/0/0 out-labels 33 44 55 -An MPLS tunnel is effectively an LSP with an associated interface. The LSP can be -described by any next-hop type (recursive, non-recursive etc), e.g.: +and to then have that created tunnel to perform ECMP: -mpls tunnel add via 10.10.10.10 GigabitEthernet0/8/0 out-label 66 -IP routes and/or MPLS x-connects can be routed via the interface, e.g. +.. code-block:: console + + $ mpls tunnel add mpls-tunnel0 via 10.10.10.11 GigEthernet0/0/0 out-labels 66 77 88 + +use .. code-block:: console - $ ip route add 2.2.2.0/24 via mpls-tunnel0 + $ sh mpls tunnel [X] -packets matching the route for 2.2.2.0/24 would thus have label 66 imposed since -it is transmitted via the tunnel. +to see the monster you have created. + +An MPLS tunnel interface is an interface like any other and now ready +for use with the usual set of interface commands, e.g.: + +.. code-block:: console -These MPLS tunnels can be used to realise MPLS RSVP-TE tunnels. + $ set interface state mpls-tunnel0 up + $ set interface ip address mpls-tunnel0 192.168.1.1/30 + $ ip route 1.1.1.1/32 via mpls-tunnel0 |