Filtering NLRI Using Special COMMUNITY Values
Routers can use route maps to filter NLRI from being added to the BGP table, or from being sent in Updates to other routers. These route maps can match a BGP route’s COMMUNITY by using the match community {standard-list-number | expanded-list-number | community-list-name [exact]} command, which in turn references a community list. Additionally, BGP includes several reserved values for the COMMUNITY PA that allow route filtering to occur, but with less effort than is require..
Convergence in a Frame-Mode MPLS Network
An important aspect in MPLS network design is the convergence time of the network. Some MPLS applications (for example, an MPLS/VPN or BGP design based on MPLS) do not work correctly unless a labeled packet can be sent all the way through from the ingress Edge-LSR to the egress Edge-LSR. In these applications, the convergence time needed by an Interior Gateway Protocol (IGP) to converge around a failure in the core network could be increased by the label propagation delay. I..
Using a Default Set of Authentication Methods
AAA authentication configuration includes commands by which a set of authentication methods is defined. A single authentication method is exactly what it sounds like—a way to authenticate a user. For example, one method is to ask a RADIUS server to authenticate a login user; another is to let a router look at a set of locally defined username commands. A set of configuration methods represents an ordered list of authentication methods, each of which is tried in order until ..
In order to modify system log messages, you must configure the Embedded Syslog Manager (ESM) by using a combination of configuration commands and TCL scripts. First you must write a TCL script to perform a certain task and make it available via TFTP. In this simple example, the TCL script in Example 18-3 filters out a particular system log message (clear counters) and permits all other messages to be forwarded as normal. Example 18-3. delcounters.tcl # delcounters.tcl ..
Let us start with the idea that complex problems are usually broken down into modular components to facilitate understanding and to make the solution more tractable. For this purpose, data communications make use of the Open Systems Interconnection (OSI) reference model. Given the extensive coverage of this model available in other books, this book does not intend to provide a complete and exhaustive overview of the OSI reference model. Instead, this section provides a brief ..
