MPLS Traffic Engineering (TE) IS-IS Configuration

In this lesson, I’ll explain how to configure MPLS TE on your Cisco IOS routers. Before you continue, make sure you are familiar with MPLS and link-state routing protocols like OSPF and IS-IS is required. Also, you should have a basic understanding of MPLS TE as explained in the introduction lesson.

This is the topology we’ll use:

Mpls Te Pe C Router Topology

Routers PE1, P1, P2, P3, and PE2 are our MPLS core network. The CE1 and CE2 routers use regular IP routing. All routers are configured to use IS-IS L2. I use Cisco IOS Software, IOSv Software (VIOS-ADVENTERPRISEK9-M), Version 15.9(3)M4.

  • Configurations
  • CE1
  • CE2
  • P1
  • P2
  • P3
  • PE1
  • PE2

Want to take a look for yourself? Here, you will find the startup configuration of each device.

Before we continue, let’s make sure we have a label-switched path (LSP) when we send traffic from CE1 to CE2:

CE1#traceroute 7.7.7.7 source 1.1.1.1 probe 1
Type escape sequence to abort.
Tracing the route to 7.7.7.7
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.12.2 1 msec
  2 192.168.23.3 [MPLS: Label 23 Exp 0] 4 msec
  3 192.168.36.6 [MPLS: Label 19 Exp 0] 3 msec
  4 192.168.67.7 4 msec

That seems to be the case.

Configuration

Let’s find out how we configure this “regular” MPLS network into a network that supports MPLS TE. There are four main items we have to configure:

  • Enable MPLS TE support:
    • Globally
    • Interfaces
  • Configure IS-IS to support MPLS TE.
  • Configure RSVP.
  • Configure a tunnel interface.

We configure these items on all MPLS routers where you want to use MPLS TE. Let’s get started.

Global

With the global mpls traffic-eng tunnels command we enable MPLS TE globally:

PE1, P1, P2, P3, and PE2
(config)#mpls traffic-eng tunnels

Interfaces

We have to enable MPLS TE support on all interfaces where we use MPLS. Let me highlight them for you:

Mpls Te Pe C Router Topology Interfaces

This is the configuration:

PE1 and PE2
(config)#interface range GigabitEthernet 0/1 - 2
(config-if-range)#mpls traffic-eng tunnels
P1, P2, and P3
(config)#interface range GigabitEthernet 0/0 - 1
(config-if-range)#mpls traffic-eng tunnels

That’s it.

IS-IS

There are two things we need to configure for IS-IS to support MPLS TE:

  • Change the metric-style to wide to support the new TLVs.
  • Enable MPLS TE support.

The metric style has to be changed on all routers because narrow and wide are incompatible. If you don’t change this on the CE routers as well, you won’t exchange any routing information anymore in IS-IS:

CE1, PE1, P1, P2, P3, PE2, and CE2
(config)#router isis
(config-router)#metric-style wide

On the PE and P routers, we enable MPLS TE support and use the loopback 0 interface for the router ID: