Introduction

Usual labels are automatically distributed using LDP, RSPV or BGP. If a LSR is connected to a device that supports MPLS forwarding but does not support LDP, static labels can be used to maintain forwarding.

MPLS Static Labels

• LDP, RSVP or BGP can be used to dynamically distribute label bindings. After an LSR receives labels, it installs the bindings into LFIB for MPLS forwarding.
• Using Static Labels, an LSR can install label bindings for either one of the following:
  • Static labels to IPv4 prefix binding.
  • Static crossconnects of labels.
• To configure static label binding, define a static label range.
• Can't configure static labels for IPv4 VPN prefixes.
• Bindings remain in LFIB even if the next hop LSR is down.

Static Label to IPv4 Prefix Binding

• Static bindings between labels and IPv4 prefixes can be configured to support MPLS hop-by-hop forwarding through neighbor routers that do not implement LDP label distribution.

Static Crossconnect of Labels

• Static crossconnects can be configured to support MPLS Label Switched Path (LSP) midpoints when neighbor routers do not implement either the LDP or RSVP label distribution, but do implement an MPLS forwarding path.

mpls static binding ipv4 6.6.6.6 255.255.255.255 500
mpls static binding ipv4 6.6.6.6 255.255.255.255 output 10.1.56.6 600

R5#sh mpls static binding
6.6.6.6/32: Incoming label: 500
  Outgoing labels:
     10.1.56.6                600

R5#sh mpls forwarding-table 6.6.6.6
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop
Label      Label      or Tunnel Id     Switched      interface
500        600        6.6.6.6/32       590           Gi2/0      10.1.56.6

Relevant Commands

mpls label range static

To enable static label bindings, a static label range is necessary.

R1(config)#        mpls label range (min) (max) static (min-label) (max-label)

R6#sh mpls label range
Downstream Generic label region: Min/Max label: 6000/6999
Range for static labels: Min/Max label: 600/699            <---static

mpls static bindings ipv4

Configures a static MPLS label binding. First and second configures local label, while third configures outgoing label/remote label.

R1(config)#        mpls static binding ipv4 (a.b.c.d) (mask) (label)
R1(config)#        mpls static binding ipv4 (a.b.c.d) (mask) input (local-label)
R1(config)#        mpls static binding ipv4 (a.b.c.d) (mask) output (dst-ip) { (lable) | explicit-null | implicit-null }

mpls label range static

To enable static label bindings, a static label range is necessary.

R1(config)#        mpls label range (min) (max) static (min-label) (max-label)

show mpls static bindings

show mpls static bindings

R5#sh mpls static binding
6.6.6.6/32: Incoming label: 500
  Outgoing labels:
     10.1.56.6                600

Additional Resources

MPLS Static Labels - MPLS Basic MPLS Configuration Guide, Cisco IOS Release 12.2SR

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