FAQ Updated: 03.3.2006 [see bottom] General questions ----------------- Question: How do I configure MPLS? What are some resources for getting started with OPNET's MPLS models? Answer: If you have not already done so, you may wish to use the following resources. 1) Please read the MPLS white papers: 1.a) Go to www.opnet.com 1.b) Click on "Support Center" 1.c) Click on "Methodologies and Case Studies" 1.d) Please read both: "MPLS Deployment Strategies" "Representing Network Traffic" (Gives explanation for Explicit and Background traffic.) 2) Please read the MPLS User guide. This has information about the MPLS protocol in general. Help -> Product documentation -> Specialized Model user guides -> MPLS model user guide 3) The "MPLS" standard project contains information about configuring MPLS, as well as example networks. You can use the example networks just as examples or as a starting point for your network. Please: 3.a) Select "File"->"Open"->"example_networks"->"MPLS" 3.b) Double click on each of the green book icons in the "README" scenario. These contain descriptions of the protocol, overview of configuration, etc. 3.c) Use the "Scenario" menu to then switch to the example networks. 4) When running your MPLS studies, you will want to make sure you look at: 4.a) Any simulation logs that are reported. To view the simulation log, right-click in the background of the Project Editor and select "Open DES Log". The simulation log reports on misconfigurations, errors, as well as notifying you of non-errors that are potentially important. Question: What are the basic steps in configuring MPLS Answer: 1. Enable MPLS on the connected interfaces 2. Configure Loopback interfaces (use OSPF, auto-assign IP addresses) 3. Create dynamic LSPs (use palette) 4. Update LSP: Protocols -> MPLS -> Update LSP details 5. Insert MPLS Config object 6. In MPLS Config: define FEC specification and Traffic Trunk profile 7. On the ingress LER: - Define the Traffic mapping Config - For Traffic assignment mode use IGP shortcuts 10.On each LSP (if dynamic) enable the Announce IGP shortcuts attribute Question: How can I identify what router interface or switch port a link is connected to in IT Guru? Answer: 1) First, look for the port names. You have two methods: i) Right-click on the link that connects the router interface and select Edit Ports. It will display both interfaces that are connected. ii) Position your mouse on the link and a tool tip will display the port names. You will see a list that contains: port a = ... port b = ... 2) Identify the interface number by viewing port attribute values. The interface number is in parenthesis. The convention for numbering interfaces is " (IF P)". For example "My_Router.PPP (IF18 P2)" refers to interface 18, port 2. 3) The number is the interface number and corresponds to the row in "IP Routing Parameters" attribute and "BGP/EIGRP/IGRP/LDP/MPLS/OSPF/RIP/RSVP Parameters" attributes in a router node. The number corresponds to the row in "Switch Port Configuration" attribute in a switch node. Note that the row number starts at zero! You can also look for "show_ca_count" in "Edit- >Preferences" menu and enable the preference. This will make row number appear in any compound attribute such as "IP Routing Parameters" and make your life easier to find the row corresponding to the interface. Question: No traffic is flowing over my MPLS LSPs. Why would this happen? Answer: First, if you haven't already done so, make sure you update the LSP details by choosing "Update LSP Details" from the "MPLS" submenu of the "Protocols" menu. This will automatically set the "Path Details" attribute of the LSPs. After this is done, the color of the LSPs will change from the default green to indicate that it has been fully configured. Second, if you are using dynamic LSPs and you are using CR-LDP as LSP signaling protocol, then make sure the simulation attribute "LDP Discovery Start Time" is not set to "Do Not Start". Dynamic LSPs rely on LDP discovery to set themselves up, so it needs to have a numeric start time (for example, 100 seconds in to the simulation). If you are using RSVP as LSP signaling protocol, then you do not need to set this attribute. Third, make sure that you have configured " MPLS Parameters->Traffic Engineering Configurations" correctly and traffic flowing over the LSP satisfies the FEC used. Question: How do I create a VPN network from scratch (using the VPN Wizard)? I created a VPN network using the VPN wizard but I see incorrect results. Answer: The VPN Wizard peforms only VPN related configuration in the network. In addition, it also sets up Label Switched Paths (LSPs) between the Provider Edge routers. The following are the actual tasks the VPN Wizard performs: - IBGP peering of Provider Edge routers - Autonomous System numbers for the Provider (P) and Provider Edge (PE) routers - LSPs between the various PEs - VRF configuration on the PEs (routing instances, interfaces, routing protocols and VRF table export) The VPN wizard does not do the following: - Addresses, routing protocols and MPLS configuration in the core network If you are configuring a network from scratch, these are the tasks you need to perform: - Assign addresses to all the physical interfaces. - Configure OSPF as the routing protocol in the network. - Create loopback interfaces on all the routers so that the Provider Edge nodes use loopback addresses for peering. - Enable MPLS in the network. - Select all routers and assign Autonomous System numbers (be careful what numbers you choose!!). - At this point, you can run the VPN Wizard to configure VPNs in your network. Miscellaneous (updated 03.3.2006) ------------- * There is no need to include separate server for each site since LAN object has embedded one. * Be careful when assigning upstream and downstream ADSL links! Check that direction is correct. * Routers that are the source or destination of an LSPs must have a loopback interface that is reachable from other sections of the MPLS domain. * When you set up an LSP be sure to use the dynamic LSP model. * For traffic mappings use: IGP shortcuts * If you need to assign IP-addresses to some interfaces (in case that you add new nodes to the exsisting network), you may use AutoAssignment, as long as you do not erase the existing addresses (apply it strictly to the specified nodes). Check from the router configurations (or Network browser) that IP-addresses were really created in the right interfaces. Be very careful! [new] * In order to make use of the IP VPN tunnels, on each client site (LAN) you have to define the MTU (Maximum Transfer Unit) size. The default value is set to ethernet (1500 bytes), however when tunnel header (20 bytes) is appended to the packet, the size exceeds the maximum supported value and packets should be fragmented. Unfortunatelly, IT Guru does not support fragmentation in this case, so packets are dropped. * When defining the Destination preferences for each application, be sure to specify the Symbolic name of the server (as shown in the exercise description), otherwise DES log will be filled with errors - destination unreachable. Reason for that is: application without defined destination preference tries to connect to the nearest site supporting that service, no matter if there is route to that site or not.