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The MPLS static feature enables you to statically assign local labels to an IPv4 prefix per VRF. Also, Label Switched Paths (LSPs) can be provisioned for these static labels by specifying the next-hop information that is required to forward the packets containing static label.
If there is any discrepancy between labels assigned statically and dynamically, the router issues a warning message in the console log. By means of this warning message, the discrepancy can be identified and resolved.
Release |
Modification |
---|---|
Release 5.1.1 |
This feature was introduced. |
By default, MPLS encapsulation is disabled on all interfaces. MPLS encapsulation has to be explicitly enabled on all ingress and egress MPLS interfaces through which the static MPLS labeled traffic travels.
1.
configure
2.
mpls
static
3.
interface
interface
4.
commit
RP/0/RP0/CPU0:router# show mpls interfaces
Mon May 12 06:21:30.937 DST
Interface LDP Tunnel Static Enabled
-------------------------- -------- -------- -------- --------
GigabitEthernet0/0/0/3 No No Yes Yes
For the interface on which MPLS static is enabled, the "Static"
column displays "Yes".
The MPLS label range configuration defines the dynamic label range. Any label that falls outside this dynamic range is available for manually allocating as static labels. The router does not verify statically-configured labels against the specified label range. Therefore, to prevent label discrepancy, ensure that you do not configure static MPLS labels that fall within the dynamic label range.
Note | The allocable range for MPLS labels is from 16 to 1048575. Label values from 0 to15 are reserved according to RFC-3032. |
1.
configure
2.
mpls
label
range
minimum_value
maximum_value
3.
commit
In this task, a static MPLS LSP is setup for a specific ingress label.
1.
configure
2.
mpls
static
3.
address-family
ipv4
unicast
4.
local-label
label-value
allocate
5.
forward
path
path_id
nexthop
nexthop_address
interface_type
interface_id
out-label
outgoing_label
6.
commit
Static MPLS label bindings for IP prefixes are used by MPLS applications such as Label Distribution Protocol (LDP) or Border Gateway Protocol (BGP) for MPLS switching. It is possible to define a static LSP for the static label.
1.
configure
2.
mpls
static
3.
address-family
ipv4
unicast
4.
local-label
label-value
allocate
per-prefix
IPv4_prefix_entry
5.
forward
path
path_id
nexthop
nexthop_address
out-label
outgoing_label
6.
commit
Note | When a static MPLS label is allocated to an IP prefix for a specific VRF, it is not possible to define a static LSP for that static label. |
1.
configure
2.
mpls
static
3.
vrf
vrf_name
address-family
ipv4
unicast
4.
5.
commit
These are the show commands that can be used to verify MPLS static bindings and LSPs.
1.
show
mpls
static
local-label
label_value
2.
show
mpls
label
range
3.
show
mpls
lsd
forwarding
During configuring or de-configuring static labels or a label range, a label discrepancy can get generated when:
Complete these steps to identify and clear the discrepancies.