Route Map Rules for NLRI Filtering

The overall logic used by route maps to filter NLRIs is relatively straightforward—the Update is compared to the route map and the route is filtered (or not) based on the first-matching clause. However, route maps can cause a bit of confusion on a couple of points; the next page or so points out some of the potential confusing points with regard to route maps when they are used to filter BGP routes. Both the route map and any referenced ACL or prefix list have deny and per..

OSI Layering Concepts and Benefits

Many benefits can be gained by defining protocol functions in layers, and then defining standard interfaces between those layers. The layers break a large, complex set of concepts and protocols into smaller pieces, making the complex set easier to talk about, easier to implement with hardware and software, and easier to troubleshoot. The following list summarizes the benefits of layered protocol specifications: ■ Easier to learn—Humans can more easily discuss and learn a..

Topology Changes without Feasible Successor

Figure 8-4 shows a case in which there is no feasible successor.   Figure 8-4. Convergence without a Feasible Successor   If the link between router 2 and router 4 fails in Figure 8-4, router 4 will become active for destination N because it has no feasible successors.   Router 4 will send a query to router 3 and router 5. Both of these routers have no feasible successors, so they become active for destination N. Because router 3 and router..

Ensuring the ELANs Are Functional between the Source and the Destination

If you configure the ELANs correctly, you should be able to ping each of the interfaces for each MPS and NHS along the default path between the source and destination client. If not, you either configured the ELAN incorrectly, you have a Layer 3 issue such as a bad IP address, or you have some routing protocol issues. Examine your intra-ELAN connectivity first. See if you can ping the neighbor device(s) within the ELAN. If you can, ping the next device in the next ELAN, eith..

Using SNMP to Extract Inventory Information from a List of Routers

The following Perl script extracts important router informationsuch as router name, physical location, contact name, and serial number from a list of routersand creates a report of this information. The script is intended to be run manually, and no arguments are required or expected. Here's some example output: Freebsd% ./inventory.pl   Router             Location        ..