Differentiated Packet Servicing
Conventional IP packet forwarding uses only the IP destination address contained within the Layer 3 header within a packet to make a forwarding decision. The hop-by-hop destination-only paradigm used today prevents a number of innovative approaches to network design and traffic flow optimization. In Figure C-2, for example, the direct link between the San Francisco core router and the Washington core router forwards the traffic entering the network in any of the Bay Area Poin..
Different Types of Adjacencies
There are several types of adjacencies: Null adjacency Packets destined for null-interface are dropped. This is used for dropping packets to unknown destinations. It can be used as an effective form of access filtering. Glean adjacency When a router is connected to a subnet, the FIB table maintains a prefix for the subnet rather than for each individual host. This subnet prefix points to a glean adjacency. When a packet must be..
Using SNMP to Perform Mass Configuration Changes
The following Perl script will distribute configuration commands to a large number of routers. It works by using SNMP to trigger TFTP file transfers into the routers. In effect, this script lets you automatically distribute a series configuration commands to a list of routers. Automating routine changes like this saves time and effort, but more importantly, it virtually eliminates typographical mistakes. Here's some example output: Freebsd% ./snmpcfg.pl =====================..
You can use OSPF to exchange customer routing information between the CE and PE routers at each site. For this example, we will configure OSPF for the CE to PE IGP at Customer A's Sites 1 and 2, but not 3, so that we can show some of the idiosyncrasies of MP-BGP route redistribution. First we will configure the CE routers. We will use two OSPF network statements on the router at Site 1. The first, 192.168.1.0/24, allows this router to communicate with the PE router, while th..
All this effort to define LSA types, create areas, and fully flood the LSAs has one goal in mind: to allow all routers in that area to calculate the best, loop-free routes for all known subnets. Although the database exchange process may seem laborious, the process by which SPF calculates the best routes requires a little less thought, at least to the level re- quired for the CCNP ROUTE exam. In fact, the choice of the best route for a given subnet, and calculated by a ..
