Configuring Multiprotocol Label Switching
Configuring MPLS Traffic Engineering
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Cisco IOS Switching Services Configuration Guide
Configuring MPLS Traffic Engineering
Perform the following tasks before enabling MPLS traffic engineering:
• Configure MPLS tunnels
• Enable Cisco Express Forwarding (CEF)
• Enable IS-IS
Perform the tasks in the following sections to configure MPLS traffic engineering:
• Configuring a Device to Support Tunnels
• Configuring an Interface to Support RSVP-based Tunnel Signalling and IGP Flooding
• Configuring an MPLS Traffic Engineering Tunnel
• Configuring IS-IS for MPLS Traffic Engineering
Step 4
Router(config)# access-list 2 permit R1
Router(config)# no tag-switching advertise-tags for 1
Router(config)# tag-switching advertise-tags for 1 to 2
Router(config)# exit
Configures R3 by defining an access list and
by instructing the router to distribute labels
for the networks permitted by access list 1
(created as part of Case 2) to the routers
permitted by access list 2.
The access list 2 permit R1 command
permits R1 and denies all other routers.
(Enter the actual network address and
netmask inplace of permit R1. For example,
access-list 1 permit 192.5.34.0 0.0.0.255.)
Step 5
Router(config)# access-list 1 permit A
Router(config)# access-list 2 permit R1
Router(config)# tag-switching advertise-tags for 1 to 2
Router(config)# exit
Configures R3.
(Enter the actual network address and
netmask inplace of permit R1. For example,
access-list 1 permit 192.5.34.0 0.0.0.255.)
Step 6
Router(config)# access-list 1 permit A
Router(config)# access-list 2 permit R3
Router(config)# tag-switching advertise-tags for 1 to 2
Router(config)# exit
Configures R4.
(Enter the actual network address and
netmask inplace of permit R1. For example,
access-list 1 permit 192.5.34.0 0.0.0.255.)
Step 7
Router(config)# access-list 1 permit A
Router(config)# access-list 2 permit R4
Router(config)# tag-switching advertise-tags for 1 to 2
Router(config)# exit
Configures R6.
(Enter the actual network address and
netmask inplace of permit R1. For example,
access-list 1 permit 192.5.34.0 0.0.0.255.)
Step 8
Router(config)# access-list 1 permit A
Router(config)# access-list 2 permit R6
Router(config)# tag-switching advertise-tags for 1 to 2
Router(config)# exit
Configures R7.
(Enter the actual network address and
netmask inplace of permit R1. For example,
access-list 1 permit 192.5.34.0 0.0.0.255.)
Command Purpose
Configuring Multiprotocol Label Switching
Configuring MPLS Traffic Engineering
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Cisco IOS Switching Services Configuration Guide
Configuring a Device to Support Tunnels
To configure a device to support tunnels, use the following commands in configuration mode:
Configuring an Interface to Support RSVP-based Tunnel Signalling and IGP
Flooding
To configure an interface to support RSVP-based tunnel signalling and IGP flooding, use the following
commands in interface configuration mode:
Note You need to enable the tunnel feature and specify the amount of reservable RSVP
bandwidth if you have an interface that supports MPLS traffic engineering.
Command Purpose
Step 1
Router(config)# ip cef
Enables standard CEF operation.
For information about CEF configuration and command
syntax, see the Cisco IOS Switching Services
Configuration Guide and Cisco IOS Switching Services
Command Reference.
Step 2
Router(config)# mpls traffic-eng tunnels
Enables the MPLS traffic engineering tunnel feature on a
device.
Command Purpose
Step 1
Router(config-if)# mpls traffic-eng tunnels
Enables the MPLS traffic engineering tunnel feature on an
interface.
Step 2
Router(config-if)# ip rsvp bandwidth
bandwidth
Enables RSVP for IP on an interface and specify amount
of bandwidth to be reserved.
For a description of IP RSVP command syntax, see the
Cisco IOS Quality of Service Command Reference.
Configuring Multiprotocol Label Switching
Configuring MPLS Traffic Engineering
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Cisco IOS Switching Services Configuration Guide
Configuring an MPLS Traffic Engineering Tunnel
To configure an MPLS traffic engineering tunnel, use the following commands in interface configuration
mode. This tunnel has two path setup options—a preferred explicit path and a backup dynamic path.
Configuring IS-IS for MPLS Traffic Engineering
To configure IS-IS for MPLS Traffic engineering, use the following IS-IS traffic engineering commands
in interface configuration mode. For a description of IS-IS commands (excluding the IS-IS traffic
engineering commands), see the Cisco IOS IP and IP Routing Configuration Guide.
Command Purpose
Step 1
Router(config)# interface tunnel1
Configures an interface type and enter interface
configuration mode.
Step 2
Router(config-if)# tunnel destination
A.B.C.D
Specifies the destination for a tunnel.
Step 3
Router(config-if)# tunnel mode mpls traffic-eng
Sets encapsulation mode of the tunnel to MPLS traffic
engineering.
Step 4
Router(config-if)# tunnel mpls traffic-eng
bandwidth
bandwidth
Configures bandwidth for the MPLS traffic engineering
tunnel.
Step 5
Router(config-if)# tunnel mpls traffic-eng
path-option 1 explicit name test
Configures a named IP explicit path.
Step 6
Router(config-if)# tunnel mpls traffic-eng
path-option 2 dynamic
Configures a backup path to be dynamically calculated
from the traffic engineering topology database.
Command Purpose
Step 1
Router(config)# router isis
Enables IS-IS routing and specify an IS-IS process for IP,
which places you in router configuration mode.
Step 2
Router(config-router)# mpls traffic-eng level 1
Turns on MPLS traffic engineering for IS-IS level 1.
Step 3
Router(config-router)# mpls traffic-eng
router-id loopback0
Specifies the traffic engineering router identifier for the
node to be the IP address associated with interface
loopback0.
Step 4
Router(config-router)# metric-style wide
Configures a router to generate and accept only new-style
TLVs.
Configuring Multiprotocol Label Switching
Configuring MPLS Traffic Engineering Paths
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Cisco IOS Switching Services Configuration Guide
Configuring MPLS Traffic Engineering Paths
This section describes two sample examples supported by traffic engineering. These cases show how you
can engineer traffic across a path in the network and establish a backup route for that traffic engineered
path (see Table 17).
In both cases, the assumption is made that traffic from R1 and R2 (in Figure 22), which is intended for
R11, would be directed by Layer 3 routing along the “upper” path R3-R4-R7-R10-R11.
Figure 22 shows a router-only MPLS network with traffic engineered paths.
Figure 22 Sample MPLS Network with Traffic Engineered Paths
Example 1—Engineer Traffic Across a Path
The following table lists the configuration commands you need to engineer traffic across the “middle”
path R3-R5-R8 by building a tunnel R1-R3-R5-R8-R10, without affecting the path taken by traffic from
R2 (see Figure 22).
Table 17 Sample Traffic Engineering Examples
This case Describes
Example 1—Engineer traffic
across a path
The steps necessary to engineer traffic across the “middle” path
R3-R5-R8 (see Figure 22).
Example 2—Establish a backup
path
The steps necessary for establishing a backup traffic engineering
route for the engineered traffic for Case 1.
Network A
S6300
R1
R2
R6 R9
R4
R5
R3
R7
R8
R10
R11
e0/1
e0/1
e0/2
e0/1
e0/1
e0/2
e0/2
e0/1
e0/1
e0/1
e0/2e0/3
e0/1
e0/2
e0/1
e0/2
e0/5 e0/4
e0/2
e0/1
e0/2
e0/2
e0/2
e0/4
e0/3
e0/1
Configuring Multiprotocol Label Switching
Configuring MPLS Traffic Engineering Paths
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Cisco IOS Switching Services Configuration Guide
To engineer traffic across a path, use the following commands in router configuration mode:
Command Purpose
Step 1
At R1:
Router(config)# ip cef distributed
Router(config)# tag-switching tsp-tunnels
Router(config)# interface e0/1
Router(config-if)# tag-switching tsp-tunnels
Router(config-if)# exit
At R3:
Router(config)# ip cef distributed
Router(config)# tag-switching tsp-tunnels
Router(config)# interface e0/1
Router(config-if)# tag-switching tsp-tunnels
Router(config-if)# exit
Router(config)# interface e0/3
Router(config-if)# tag-switching tsp-tunnels
Router(config-if)# exit
At R5 and R8:
Router(config)# ip cef distributed
Router(config)# tag-switching tsp-tunnels
Router(config)# interface e0/1
Router(config-if)# tag-switching tsp-tunnels
Router(config-if)# exit
Router(config)# interface e0/2
Router(config-if)# tag-switching tsp-tunnels
Router(config-if)# exit
At R10:
Router(config)# ip cef distributed
Router(config)# tag-switching tsp-tunnels
Router(config)# interface e0/1
Router(config-if)# tag-switching tsp-tunnels
Router(config-if)# exit
Configures support for LSP tunnel signaling
along the path.
In order to configure distributed VIP MPLS,
you must configure distributed CEF switching.
Enter the ip cef distributed command on all
routers.
Note To configure a Cisco 7200 series router,
enter ip cef. To configure a Cisco 7500
series router, enter ip cef distributed.
Step 2
At R1:
Router(config)# interface tunnel 2003
Router(config-if)# ip unnumbered e0/1
Router(config-if)# tunnel mode tag-switching
Router(config-if)# tunnel tsp-hop 1 10.10.0.103
Router(config-if)# tunnel tsp-hop 2 10.11.0.105
Router(config-if)# tunnel tsp-hop 3 10.12.0.108
Router(config-if)# tunnel tsp-hop 4 10.13.0.110 lasthop
Router(config-if)# exit
Configures a LSP tunnel at the headend.
(IP address of R3:e0/1)
(IP address of R5:e0/1)
(IP address of R8:e0/1)
(IP address of R10:e0/1)
Step 3
At R1:
Router(config)# router traffic-engineering
Router(config)# traffic-engineering filter 1 egress
10.14.0.111 255.255.255.255
Configures the traffic engineering filter to
classify the traffic to be routed.
The filter selects all traffic where the
autonomous system (AS) egress router is
10.14.0.111(10.14.0.111 is the IP address of
R11:e0/1).
Step 4
At R1:
Router(config)# router traffic-engineering
Router(config)# traffic-engineering route 1 tunnel 2003
Configures the traffic engineering route to send
the engineered traffic down the tunnel.
Configuring Multiprotocol Label Switching
Configuring MPLS Virtual Private Networks
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Cisco IOS Switching Services Configuration Guide
Example 2—Establish a Backup Path
Example 2 involves establishing a backup traffic engineering route for the engineered traffic for Case 1.
This backup route uses the “lower” path. The backup route uses a tunnel R1-R3-R6 and relies on Layer 3
routing to deliver the packet from R6 to R11.
To set up a traffic engineering backup path (assuming Case 1 steps have been performed), use the
following commands in router configuration mode:
Configuring MPLS Virtual Private Networks
Perform the tasks in the following sections to configure and verify VPNs:
• Defining VPNs
• Configuring BGP Routing Sessions
• Configuring PE to PE Routing Sessions
• Configuring BGP PE to CE Routing Sessions
• Configuring RIP PE to CE Routing Sessions
• Configuring Static Route PE to CE Routing Sessions
• Verifying VPN Operation
Command Purpose
Step 1
At R6:
Router(config)# ip cef distributed
Router(config)# tag-switching tsp-tunnels
Router(config)# interface e0/1
Router(config-if)# tag-switching tsp-tunnels
Router(config-if)# exit
At R3:
Router(config)# ip cef distributed
Router(config)# tag-switching tsp-tunnels
Router(config)# interface e0/4
Router(config-if)# tag-switching tsp-tunnels
Router(config-if)# exit
Enables LSP tunnel signalling along the path
(where such signalling is not already
enabled).
Step 2
At R1:
Router(config)# interface tunnel 2004
Router(config-if)# ip unnumbered e0/1
Router(config-if)# tunnel mode tag-switching
Router(config-if)# tunnel tsp-hop 1 10.10.0.103
Router(config-if)# tunnel tsp-hop 2 10.21.0.106 lasthop
Router(config-if)# exit
Configures the LSP tunnel at the headend.
(IP address of R3:e0/1)
(IP address of R6:e0/1)
Step 3
At R1:
Router(config)# router traffic-engineering
Router(config)# traffic-engineering route 1 tunnel 2004
pref 200
Configures the traffic engineering route to
send the engineered traffic down the tunnel if
the middle path (Case 1 route) is unavailable.
Configuring Multiprotocol Label Switching
Configuring MPLS Virtual Private Networks
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Defining VPNs
To define VPN routing instances, use the following commands in router configuration mode on the PE
router:
Configuring BGP Routing Sessions
To configure BGP routing sessions in a provider network, use the following commands in router
configuration mode on the PE router:
Configuring PE to PE Routing Sessions
To configure PE to PE routing sessions in a provider network, use the following commands in router
configuration mode on the PE router:
Command Purpose
Step 1
Router(config)# ip vrf
vrf-name
Enters VRF configuration mode and define the
VPN routing instance by assigning a VRF name.
Step 2
Router(config-vrf)# rd
route-distinguisher
Creates routing and forwarding tables.
Step 3
Router(config-vrf)# route-target {import | export |
both}
route-target-ext-community
Creates a list of import and/or export route target
communities for the specified VRF.
Step 4
Router(config-vrf)# import map
route-map
(Optional) Associates the specified route map
with the VRF.
Step 5
Router(config-if)# ip vrf forwarding
vrf-name
Associates a VRF with an interface or
subinterface.
Command Purpose
Step 1
Router(config)# router bgp
autonomous-system
Configures the BGP routing process with the
autonomous system number passed along to other
BGP routers.
Step 2
Router(config-router)# neighbor {
ip-address
|
peer-group-name
} remote-as
number
Specifies a neighbor’s IP address or BGP peer
group identifying it to the local autonomous
system.
Step 3
Router(config-router)# neighbor
ip-address
activate
Activates the advertisement of the IPv4 address
family.
Command Purpose
Step 1
Router(config-router)# address-family vpnv4 [unicast |
multicast]
Defines IBGP parameters for VPNv4 NLRI
exchange.
Step 2
Router(config-router-af)# neighbor
address
remote-as
as-number
Defines an IBGP session to exchange VPNv4
NLRIs.
Step 3
Router(config-router-af)# neighbor
address
activate
Activates the advertisement of the IPv4 address
family.
Configuring Multiprotocol Label Switching
Configuring MPLS Virtual Private Networks
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Configuring BGP PE to CE Routing Sessions
To configure BGP PE to CE routing sessions, use the following commands in router configuration mode
on the PE router:
Configuring RIP PE to CE Routing Sessions
To configure RIP PE to CE routing sessions, use the following commands in router configuration mode
on the PE router:
Command Purpose
Step 1
Router(config-router)# address-family ipv4 [unicast]
vrf
vrf-name
Defines EBGP parameters for PE to CE routing
sessions.
Note The default is Off for auto-summary and
synchronization in the VRF
address-family submode.
Step 2
Router(config-router-af)# neighbor
address remote-as
as-number
Defines an EBGP session between PE and CE
routers.
Step 3
Router(config-router-af)# neighbor
address
activate
Activates the advertisement of the IPv4 address
family.
Command Purpose
Step 1
Router(config)# router rip
Enables RIP.
Step 2
Router(config-router-af)# address-family ipv4
[unicast] vrf
vrf-name
Defines RIP parameters for PE to CE routing
sessions.
Note The default is Off for auto-summary and
synchronization in the VRF
address-family submode.
Step 3
Router(config-router-af)# network
prefix
Enables RIP on the PE to CE link.
Configuring Multiprotocol Label Switching
Configuring MPLS Virtual Private Networks
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Configuring Static Route PE to CE Routing Sessions
To configure static route PE to CE routing sessions, use the following commands in router configuration
mode on the PE router:
Verifying VPN Operation
To verify VPN operation by displaying routing information on the PE routers, use any of the following
show commands in any order:
Command Purpose
Step 1
Router(config)# ip route vrf
vrf-name
Defines static route parameters for every PE to CE
session.
Step 2
Router(config-router)# address-family ipv4 [unicast]
vrf
vrf-name
Defines static route parameters for every BGP PE
to CE routing session.
Note The default is Off for auto-summary and
synchronization in the VRF
address-family submode.
Step 3
Router(config-router-af)# redistribute static
Redistributes VRF static routes into the VRF BGP
table.
Step 4
Router(config-router-af)# redistribute static
connected
Redistributes directly connected networks into the
VRF BGP table.
Command Purpose
Router# show ip vrf
Displays the set of defined VRFs and interfaces.
Router# show ip vrf [{brief | detail | interfaces}]
vrf-name
Displays information about defined VRFs and
associated interfaces.
Router# show ip route vrf
vrf-name
Displays the IP routing table for a VRF.
Router# show ip protocols vrf
vrf-name
Displays the routing protocol information for a VRF.
Router# show ip cef vrf
vrf-name
Displays the CEF forwarding table associated with a
VRF.
Router# show ip interface
interface-number
Displays the VRF table associated with an interface.
Router# show ip bgp vpnv4 all [tags]
Displays information about all BGP VPN-IPv4
prefixes.
Router# show tag-switching forwarding vrf
vrf-name
[
prefix
mask/length
][detail]
Displays label forwarding entries that correspond to
VRF routes advertised by this router.
Configuring Multiprotocol Label Switching
Configuring MPLS CoS Backbone Support
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Cisco IOS Switching Services Configuration Guide
Configuring MPLS CoS Backbone Support
Several different methods exist for supporting CoS across an MPLS backbone, the choice depending on
whether the core has label switch routers (LSRs) or ATM LSRs. In each case, however, the CoS building
blocks are the same: CAR, WRED, and WFQ.
Three configurations are described below:
• LSRs used at the core of the network backbone
• ATM LSRs used at the core of the network backbone
• ATM switches without the MPLS feature enabled
LSRs
LSRs at the core of the MPLS backbone are usually either Cisco 7200 and Cisco 7500 series routers
running MPLS software. Packets are processed as follows:
1. IP packets enter into the edge of the MPLS network.
2. The edge LSRs invoke CAR to classify the IP packets and possibly set IP precedence. Alternatively,
IP packets can be received with their IP precedence already set.
3. For each packet, the router performs a lookup on the IP address to determine the next-hop LSR.
4. The appropriate label is placed on the packet with the IP precedence bits copied into every label
entry in the MPLS header.
5. The labeled packet is then forwarded to the appropriate output interface for processing.
6. The packets are differentiated by class. This is done according to drop probability (WRED) or
according to bandwidth and delay (WFQ). In either case, LSRs enforce the defined differentiation
by continuing to employ WRED or WFQ on each hop.
ATM LSRs
ATM LSRs at the core implement the multiple label virtual circuit model (LVC). In the multiple LVC
model, one label is assigned for each service class for each destination. The operation of the edge LSR
is the same as that described previously for the LSR case, except that the output is an ATM interface.
WRED is used to define service classes and determine discard policy during congestion.
In the multiple LVC model, however, class-based WFQ is used to define the amount of bandwidth
available to each service class. Packets are scheduled by class during congestion. The ATM LSRs
participate in the differentiation of classes with WFQ and intelligently drop packets when congestion
occurs. The mechanism for this discard activity is weighted early packet discard (WEPD).
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