Cisco Labs – Redundant and Resilient networks (13) – MPLS – AToM – HDLC, PPP over MPLS


Introduction

During my university studies I was doing a diploma thesis in field of Redundant and reliable networking. The purpose of itwas to create LAB examples for students, so they can test First Hop Redundancy Protocols (FHRP) , Any Transport over MPLS (AToM) and Border Gateway Protocol (BGP) on Cisco platform. These tasks are created to Virtlab (Virtual lab with physical Cisco routers) however configuration is valid and tested on physical Cisco routers as well.

Each task in the series will have its separate post with brief description of the task and schema. Complete task can be downloaded on My Skydrive

ZIP file contains:

  • *.HTML file – complete step by step guide how to perform the task
  • *.PNG – pictures with topology and others
  • *_preconf.txt – file with basic configuration of topology to be able to focus on task goal (IP addresses, interfaces and so on)
  • *_end.txt – file with complete configuration. Once put to the routers, you will get working task
  • *.dia – Topology in free DIA editor
  • *.XML – topology in XML format

To complete the task:

  • Connect your environment accorrding the topology
  • open the file *_preconf.txt from ZIP file with complete task and configure your environment with basic settings so you can start with the task.



MPLS – AToM – HDLC,PPP over MPLS

Title: MPLS – AToM – HDLC,PPP over MPLS

Goal:

  • Configure AToM to transport HDLC encapsulated traffic over the MPLS-based core network.
  • Change HDLC encapsulation to PPP and test function.

Required time: 120 minutes

Theoretical background:

Links related to this task:

Topology:

MPLS-AToM-HDLC,PPP

Configuration:

 

1) Check pre-configured settings

Before starting configuration of HDLC or PPP you should check pre-configured settings. First use ping command to test connectivity between PE1 and PE3 routers.

Also check OSPF if networks are propagated correctly.

Use following commands on core routers PE1, P, PE3 and check results.

      Pxx#show mpls ldp binding; display LDP bindings on the router
      Pxx#show mpls ldp discovery; show discovered MPLS enabled routers
      Pxx#show mpls ldp neighbor; show to which neighbors router established TCP sessions
      Pxx#show mpls forwarding-table; display forwarding table of local and remote labels. 

2) AToM configuration – customer side

Customer’s side routers CE1,CE2 must be configured, that interfaces facing MPLS core network have IP addresses and as same encapsulation as on providers side.

Router CE1

      CE1(config)#interface #CE1:CE1-PE1#
      CE1(config-if)#encapsulation hdlc; encapsulate traffic using HDLC (by default) 
      CE1(config-if)#ip address 100.0.0.1 255.255.255.0; IP address from the as same subnet as on CE2 router
      CE1(config-if)#no shutdown

Router CE2

      CE2(config)#interface #CE2:PE3-CE2#
      CE2(config-if)#ip address 100.0.0.2 255.255.255.0; IP address from as same subnet as on CE1 router
      CE2(config-if)#encapsulation hdlc; encapsulate traffic using HDLC (by default) 
      CE2(config-if)#no shutdown

3) AToM configuration – provider side

Router PE1

      PE1(config)#interface #PE1:CE1-PE1#
      PE1(config-if)#encapsulation hdlc; encapsulate traffic using HDLC (default) 
      PE1(config-if)#clock rate 64000
      PE1(config-if)#no shutdown
      PE1(config-if)#xconnect 40.0.0.1 100 encapsulation mpls; create VC 100 to transfer HDLC traffic through MPLS core 

VC on MPLS is unidirectional. To configure l2 transport tunnel we need to configure VC 100 on both provider edge routers (PE1, PE3).

Router P

Router P needs to have only basic MPLS configured.

Router PE3

      PE3(config)#interface #PE3:PE3-CE2#
      PE3(config-if)#encapsulation hdlc; encapsulate traffic using HDLC (default) 
      PE3(config-if)#clock rate 64000
      PE3(config-if)#no shutdown
      PE3(config-if)#xconnect 20.0.0.1 100 encapsulation mpls; create VC 100 to transfer HDLC traffic through MPLS core 

4) Go through Function test and then continue point 5)

5) Change encapsulation to PPP

Shut down serial interface on CE1, CE2, PE1, PE3 before changing encapsulation to PPP.

      CE1(config)#interface #CE1:CE1-PE1#
      CE1(config-if)#shutdown
      CE2(config)#interface #CE2:PE3-CE2#
      CE2(config-if)#shutdown
      PE1(config)#interface #PE1:CE1-PE1#
      PE1(config-if)#shutdown
      PE3(config)#interface #PE3:PE3-CE2#
      PE3(config-if)#shutdown

Change encapsulation to PPP on CE1, CE2, PE1, PE3.

      CE1(config-if)#encapsulation ppp
      CE2(config-if)#encapsulation ppp
      PE1(config-if)#encapsulation ppp
      PE3(config-if)#encapsulation ppp

Set clock rate on PE1, PE3.

      PE1(config-if)#clock rate 64000
      PE3(config-if)#clock rate 64000

Turn on interfaces

      CE1(config-if)#no shutdown
      CE2(config-if)#no shutdown
      PE1(config-if)#no shutdown
      PE3(config-if)#no shutdown

6) Xconnect interfaces on PE1 and PE3

      PE1(config)#interface #PE1:CE1-PE1#
      PE1(config-if)#xconnect 40.0.0.1 100 encapsulation mpls; create VC 100 to transfer PPP traffic through MPLS core 
      
      PE3(config)#interface #PE3:PE3-CE2#
      PE3(config-if)#xconnect 20.0.0.1 100 encapsulation mpls; create VC 100 to transfer PPP traffic through MPLS core 

7) Go through Function test again

Function test:

1) Test MPLS functionality using ping

      PE1# ping mpls ipv4 40.0.0.1; ping command for MPLS

2) Display MPLS related information

Verify the status of virtual circuits on the routers PE1 and PE3. Notice amount of data sent through those circuits. Check VC details.

      Rx# sh mpls l2transport vc detail

3) Test connectivity

Test connectivity between CE1 and CE2 routers.

      CE1# ping 100.0.0.2
      CE1# traceroute 100.0.0.2; there is no hop between customer`s IP addresses. The MPLS core acts as single serial circuit.

4) Show CE router statistics

Run following commands on CE1 or CE2.

      CE1# sh cdp neighbor; display Cisco Discovery Protocol neighbors
      CE1# sh interface #CE1:CE1-PE1#; display detail statistics of an interface

5) debug MPLS AToM events

Run following commands on the PE1 or PE3.

      PE1# debug mpls l2transport vc event; display debug information related to l2transport tunnel in MPLS core network 

Then go to PE1 console and shut interface facing to CE1 router #PE1:CE1-PE1# down. This will cause the VC 100 to break.

    PE3#
    *Nov 17 00:00:17.047: AToM MGR [20.0.0.1, 100]: Remote end down, vc is down
    *Nov 17 00:00:17.055: AToM MGR [20.0.0.1, 100]: Unprovision and deallocate SSM segment

Turn the interface on again.

Then go to P console and shut some interface down. This will cause the VC 100 to break.

    PE3#
    *Nov 17 00:05:39.815: %LDP-5-NBRCHG: LDP Neighbor 20.0.0.1:0 (2) is DOWN (Discovery Hello Hold Timer expired)
    *Nov 17 00:05:39.823: AToM MGR [20.0.0.1, 100]: Remote end down, vc is down

 

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