© 2006 Cisco Systems, Inc. All rights reserved. Implementing Secure Converged Wide Area Networks (ISCW) Module 4: Frame Mode MPLS Implementation

© 2006 Cisco Systems, Inc. All rights reserved. Module 4: Frame Mode MPLS Implementation Lesson 4.3: Implementing Frame Mode MPLS

© 2006 Cisco Systems, Inc. All rights reserved. Objectives  Describe the steps required to configure MPLS.  Identify the distribution protocol options when configuring MPLS.

© 2006 Cisco Systems, Inc. All rights reserved. The Procedure to Configure MPLS  Configure CEF.  Configure MPLS on a frame mode interface.  (Optional) Configure the MTU size in label switching.

© 2006 Cisco Systems, Inc. All rights reserved. Step 1: Configure CEF  To enable MPLS, you must first configure CEF:  Configure CEF: Enable CEF switching to create the FIB table. Enable CEF switching on all core interfaces.  Configure MPLS on a frame mode interface.  (Optional) Configure the MTU size in label switching.

© 2006 Cisco Systems, Inc. All rights reserved. ip cef [distributed] Router(config)# Commands for Configuring CEF  Starts CEF switching and creates the FIB table  The distributed keyword configures distributed CEF (running on VIP or line cards)  All CEF-capable interfaces run CEF switching ip route-cache cef Router(config-if)#  Enables CEF switching on an interface  Usually not needed

© 2006 Cisco Systems, Inc. All rights reserved. Using the ip cef [distributed] Parameter  The optional [distributed] parameter enables dCEF. This distributes the CEF information to the line cards and the line cards perform express forwarding.  Consider the following: CEF is enabled by default only on these platforms: Cisco 7100 series router Cisco 7200 series router Cisco 7500 series Internet router Distributed CEF is enabled on the Cisco 6500 series router. Distributed CEF is enabled on the Cisco series Internet router.

© 2006 Cisco Systems, Inc. All rights reserved. Monitoring IP CEF  Displays a summary of the FIB show ip cef detail Router# Router#show ip cef detail IP CEF with switching (Table Version 6), flags=0x0 6 routes, 0 reresolve, 0 unresolved (0 old, 0 new) 9 leaves, 11 nodes, bytes, 9 inserts, 0 invalidations 0 load sharing elements, 0 bytes, 0 references 2 CEF resets, 0 revisions of existing leaves refcounts: 543 leaf, 544 node Adjacency Table has 4 adjacencies /32, version 0, receive /32, version 3, cached adjacency to Serial0/ packets, 0 bytes tag information set local tag: 28 fast tag rewrite with Se0/0.10, point2point, tags imposed: {28} via , Serial0/0.10, 0 dependencies next hop , Serial0/0.10 valid cached adjacency tag rewrite with Se0/0.10, point2point, tags imposed: {28}

© 2006 Cisco Systems, Inc. All rights reserved. Using show ip cef Parameters ParameterDescription Unresolved(Optional) Displays unresolved FIB entries Summary(Optional) Displays a summary of the FIB Network(Optional) Displays the FIB entry for the specified destination network Mask(Optional) Displays the FIB entry for the specified destination network and mask Longer- prefixes (Optional) Displays the FIB entries for all the specific destinations Detail(Optional) Displays detailed FIB entry information type number (Optional) Lists the interface type and number for which to display FIB entries

© 2006 Cisco Systems, Inc. All rights reserved. Step 2: Configure MPLS on Frame Mode Interface  Configure CEF.  Configure MPLS on a frame mode interface: Enable label switching on a frame mode interface. Start LDP or TDP label distribution protocol.  (Optional) Configure the MTU size in label switching.

© 2006 Cisco Systems, Inc. All rights reserved. Commands for Configuring MPLS on a Frame Mode Interface  Enables label switching on a frame mode interface  Starts LDP on the interface mpls ip Router(config-if)# mpls label protocol [tdp | ldp | both] Router(config-if)#  Starts selected label distribution protocol on the specified interface

© 2006 Cisco Systems, Inc. All rights reserved. Configuring MPLS on a Frame Mode Interface: Example 1

© 2006 Cisco Systems, Inc. All rights reserved. Configuring MPLS on a Frame Mode Interface: Example 2

© 2006 Cisco Systems, Inc. All rights reserved. Step 3: Configure the MTU Size in Label Switching  Configure CEF.  Configure MPLS on a frame mode interface.  Configure the MTU size in label switching: Increase MTU on LAN interfaces.

© 2006 Cisco Systems, Inc. All rights reserved. Commands for Configuring MTU Size  Label switching increases the MTU requirements on an interface because of additional label header.  Interface MTU is automatically increased on WAN interfaces; IP MTU is automatically decreased on LAN interfaces.  Label-switching MTU can be increased on LAN interfaces (resulting in jumbo frames) to prevent IP fragmentation. mpls mtu bytes Router(config-if)#

© 2006 Cisco Systems, Inc. All rights reserved. Configuring Label Switching MTU

© 2006 Cisco Systems, Inc. All rights reserved. Summary  There are three steps to configuring an MPLS: Configure CEF:. Configure MPLS on a frame mode interface. Configure the maximum transmission unit (MTU) size in label switching.  To enable MPLS, you must first enable CEF switching. CEF switching is commonly enabled globally on a router. However, it can also be enabled on individual interfaces.  You can display entries in the FIB or display a summary of the FIB with the show ip cef command.  Cisco routers can use one or both of two protocols for distribution: Tag Distribution Protocol (TDP) Label Distribution Protocol (LDP)

© 2006 Cisco Systems, Inc. All rights reserved. Q and A

© 2006 Cisco Systems, Inc. All rights reserved. Resources  Multiprotocol Label Switching (MPLS) support_category_home.html

© 2006 Cisco Systems, Inc. All rights reserved.