Other Applications of Policy Routing
One practical application of policy routing is its use with firewalls. Firewalls are devices that apply security requirements to traffic. Firewall implementations include packet filtering, authentication, and encryption. Depending on the network setup, administrators might want to direct some or all incoming (or outgoing) traffic toward a firewall device, as shown in Figure 8-9. Figure 8-9. Incoming or Outgoing Traffic Can Be Routed to a Firewall An applicable situati..
Determining All Subnets of a Network—Binary
Another common question, typically simply a portion of a more challenging question on the CCIE written exam, relates to finding all subnets of a network. The base underlying question might be as follows: Given a particular class A, B, or C network, and a mask/prefix length used on all subnets of that network, what are the actual subnet numbers? The answers can be found using binary or using a simple decimal algorithm. This section first shows how to answer the question using..
In a typical distance vector protocol, each router advertises its table of reachable destinations (vectors) and the distances to them (distance) on each of its interfaces on a regular basis (periodic updates). OSPF routers advertise the state of their directly connected links to all routers on the network (through flooding). Although OSPF uses periodic updates, long periods of time exist between them, reducing network traffic to a minimum. Each router receives these link-stat..
STUN provides the ability to emulate an SDLC circuit through an IP network. To simply connect two SDLC or two HDLC ports on different routers, you can use the following: Stun-A#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Stun-A(config)#interface Loopback0 Stun-A(config-if)#ip address 10.1.15.5 255.255.255.252 Stun-A(config-if)#exit Stun-A(config)#stun peer-name 10.1.15.5 Stun-A(config)#stun protocol-group 1 basic Stun-A(config)#inter..
With the emergence of voice traffic into data networks, the need to differentiate between the various classes of service has become greater. PQ/CBWFQ, most commonly known as LLQ, is a new feature that provides a strict priority queue for voice traffic and a weighted fair queue for each of the other classes of traffic. LLQ brings strict priority queuing to the CBWFQ scheme. Figure 18-4 illustrates the basic concepts of how LLQ works. Figure 18-4. How LLQ Works Without ..
