Configuring Static Adjacency Segment Identifier for Aggregate Ethernet Member Links Using Single-hop Static LSP


In a network where aggregate Ethernet (AE) bundles are in use, an aggregate link could be bundle of ‘N’ number of physical link. The traffic sent over these AE bundle interfaces are forwarded on any of the member links of an AE interface. The traffic can take any physical link based on the hash defined for load-balancing the traffic, which makes it difficult to isolate which link have gone bad or dropping the traffic.

One way to test the forwarding path available in the network, including member links of an AE interface, is by adding a single-hop static LSP with the next-hop pointing to specific member link of AE interface. The default label-operation for these static LSP must be pop and forward. When a packet hits these labeled routes, the packet is forwarded on to a specific member-link. A unique label is used to identify the member link thus these labels are referred as adjacency SID and these are statically provisioned.

You can control the flow of the packets in the network by constructing a label stack in controller, which includes the labels allocated by all transit static LSP. The OAM packets are crafted and injected into the network with entire label-stack.

When a packet hits this label route the label is popped and traffic is forwarded on the member link specified in the configuration. A destination MAC is chosen while forwarding the packet, the destination Mac is the aggregate interface MAC address (selected based on nexthop address configured).

When the member link goes down and aggregate interface is up then the route corresponding to that member link is deleted. When an aggregate interface goes down then all the routes corresponding to member links of the aggregate interface is deleted. When the child physical interface is LACP detached but the child physical interface is up, the labeled route for the child link is deleted. In the case of LACP detach, the member link is up and invalid forwarding state then the OAM packets is dropped in PFE when child physical interface is detached.

The static LSP configuration is extended to accommodate the member-link name. A new CLI statement member-interface is added under the transit configuration.

A static LSP label should be configured from a defined static label range. The following is a sample configuration of static LSP label:

user@host# show protocols mpls label-range static-label-range 1000000 1048575;

The recommendation is to configure the default static label range (1000000-1048575) of Junos for the static LSP. If you wish to configure label-range other than the default static label range, then it can be done as multiple ranges can be configured.

The following is an example to configure single-hop static LSP for AE member link:

  1. Define a static label range.
    user@host# set protocols mpls label-range static-label-range 1000000 1048575;
  2. Create a static LSP for AE member link from the static label range.
    user@host# set protocols mpls static-label-switched-path statc-lsp transit 100001 pop next-hop member-interface interface-name

In this configuration, a transit labelled router is installed in mpls.0 and pops the label and forwards the packet down the next-hop. The next-hop address is mandatory for broadcast interfaces (such as ge-, xe-, ae-) and the if-name is be used for p2p interfaces (such as so-). The address is required for broadcast interfaces because the next-hop IP address is needed to pick the destination MAC address. The source MAC address for the packet is the AE’s MAC address.

The following are sample outputs to view the member link name in the next-hop output:

show mpls static-lsp extensive

user@host> show mpls static-lsp extensive

show route label label-name extensive

user@host> show route label 1000001 extensive