CCNP CCIE Complete

TABLE 3 . 1 Commands to Clear the NAT Table Command Meaning clear ip nat translation * Clears all NAT table entries. clear ip nat translation inside global-ip Clears the inside NAT translation table entry for the specified IP address. ... [full story]

Verifying and Troubleshooting the NAT Configuration There are two commands used to verify the NAT configuration on a router. The show ip nat translations command shows the translations in the NAT table: The following is an example of its output: ... [full story]

Configuring NAT for Overlapping Addresses Configuring NAT for overlapping address translation is similar to configuring dynamic NAT. The difference is you must create and apply a pool of IP addresses for the traffic to the inside of the network, as ... [full story]

Configuring TCP Load Distribution NAT has a feature that is really unrelated to getting hosts using RFC 1918 address space to be able to communicate on the Internet. Using this feature in NAT, you can establish a virtual host on ... [full story]

Configuring NAT Using Overloading Once all IP addresses in a pool have been allocated, any new connection attempts will fail. So if your ISP allocated you only 13 IP addresses, then only the first 13 users will be able to ... [full story]

Configuring Dynamic NAT Dynamic NAT is used to map inside local IP addresses to inside global IP addresses on the fly from a pool of available IP addresses. Again, you must have IP addresses assigned to the interfaces on the ... [full story]

Configuring Static NAT Static NAT is used to map a single inside global IP address to a single inside local IP address. Usually the inside local IP address is one from the RFC 1918 address space and the inside global ... [full story]

Configuring NAT In this section, we will talk about the commands needed for the following NAT configurations:  Static NAT  Dynamic NAT Configuring NAT 89  Using overloading for NAT  TCP load distribution  Translation of overlapping addresses ... [full story]

FIGURE 3 . 5 NAT translating overlapping addresses NAT Router Inside Host 221.68.20.48 www.sybex.com 221.68.20.47 DNS Server 124.1.8.14 Internet SA = 221.68.20.48 DA = 10.12.1.2 221.68.20.48 message to www.sybex.com SA = 124.1.8.14 DA = 221.68.20.48 A = 10.12.1.2 DNS response ... [full story]

Distance-Vector Protocol Scalability Issues In small networks—meaning those with fewer than 100 routers and an environment that’s much more forgiving of routing updates and calculations—distance-vector protocols perform fairly well. However, you’ll run into several problems when attempting to scale a ... [full story]

Scalability Limitations of Link-State Routing Protocols Link-state routing protocols alleviate the scalability issues faced by distance-vector protocols, because the algorithm uses a different procedure for route calculation and advertisement. This enables them to scale along with the growth of the ... [full story]

FIGURE 4 . 1 IGRP redistribution example IGRP 100 EIGRP 150 Ethernet Router1 Router2 Ethernet Router3 192.168.1.0/24 192.168.200.0/24 192.168.24.0/24 192.168.150.0/24 Here are some special features of redistribution for IGRP and EIGRP that you won’t find in other routing protocols. Redistribution ... [full story]

IGRP Configuration The basic configuration of IGRP is very straightforward. In order to initialize IGRP on a router, enter the router igrp AS# command in global configuration mode: Router(config)#router igrp ? <1-65535> Autonomous system number Once you’ve initialized IGRP on ... [full story]

FIGURE 4 . 2 Automatic redistribution example In this example, redistribution will not need to be configured. Because both IGRP and EIGRP have AS number 100, redistribution will automatically occur. If they had different AS numbers, then redistribution would have ... [full story]

IGRP Redistribution At this point, we will only briefly cover redistribution for IGRP. Redistribution will be covered in greater detail in Chapter 10. You may be wondering what redistribution is. Redistribution is the process in which routes learned by one ... [full story]

Load Balancing Load balancing is a way that a router can send traffic over multiple paths to the same destination. It is used to cut down on the amount of traffic passing over a single path to a destination. IGRP, ... [full story]

TABLE 4 . 2 Metric Association of K-Values Value Metric K1 Bandwidth K2 Loading of the link (effective bandwidth percentage used) K3 Delay K4, K5 Reliability Each constant is used to assign a weight to a specific variable. This means ... [full story]

IGRP Metrics Metrics are the mathematics used to select a route. The higher the metric associated with a route, the less desirable it is. For IGRP, the Bellman-Ford algorithm uses the following equation and creates the overall 24-bit metric assigned ... [full story]

IGRP Timers The update interval for IGRP is 90 seconds by default. IGRP uses a random factor of 20 percent to stagger updates, so the update interval is actually between 72 and 90 seconds. By default, when a route is ... [full story]

Interior Gateway Routing Protocol Interior Gateway Routing Protocol (IGRP) was developed by Cisco in the mid-1980s to overcome the distance limitations of the Routing Information Protocol (RIP). Instead of using the hop count metric like RIP, IGRP uses a composite ... [full story]

IGRP Features and Operation IGRP sends out periodic broadcasts of its entire routing table. Upon initialization, IGRP broadcasts a request out all IGRP-enabled interfaces. IGRP then performs a check on the received updates to validate that the source address of ... [full story]

FIGURE 4 . 3 IGRP configuration example This would configure IGRP for the network. If you decide to cut down on excess bandwidth usage on the Ethernet segment of Router1, you will make interface Ethernet 0 passive. Here is the ... [full story]

Configuring OSPF—Single Area (NBMA Environment) Previously, we mentioned five different possible ways to configure NBMA network interfaces. They are as follows:  Broadcast  Non-broadcast multi-access Configuring OSPF 167  Point-to-point  Point-to-multipoint broadcast  Point-to-multipoint non-broadcast We’ll outline three ... [full story]

Broadcast Configuration A full mesh among all OSPF routers is required for this environment to be configured and work properly. A full explanation of the PVC configuration is beyond the scope of this chapter, but here is a sample configuration: ... [full story]

Point-to-Multipoint This configuration does away with the assumption that there are PVCs configured for all routers creating a full mesh. The same ip ospf network command is used to specify that the network type is point-to-multipoint non-broadcast. This tells the ... [full story]

TABLE 6 . 1 LSA Types Type Code Description 1 Router LSA 2 Network LSA 3 Network Summary LSA 4 ASBR Summary LSA 5 AS External LSA 6 Group Membership LSA 7 NSSA External LSA 8 External Attributes LSA 9 ... [full story]

FIGURE 5 . 6 OSPF area topology Only two of the five configurations are shown—otherwise you would just see a lot of redundant information. Notice the very specific wildcard masks in the network statements. These facilitate the removal or addition ... [full story]

Configuring OSPF—Single Area The easiest (and least scalable) way to configure OSPF is to simply use Area 0. If all you want to configure is one area, we recommend that you use Area 0, but you can use any area ... [full story]

Broadcast Discovering the neighbors on a broadcast network is done somewhat differently. Here you will see what happens on a broadcast multi-access network: RouterA(config-if)#router ospf 1 RouterA(config-router)#network 172.16.230.0 0.0.0.255 area 0 OSPF: Interface Ethernet0 going Up OSPF: Tried to build ... [full story]

Point-to-Point Because the link described by the previous output is point-to-point, no DR/BDR election occurred; instead, each router decided which would be the master and which would be the slave. Once the master/slave roles had been established, DBD (another acronym ... [full story]

Discovering the Network with OSPF The moment OSPF is enabled on a router and networks are added to the OSPF process, the router will try to discover the OSPF neighbors on the connected links that support or simulate 160 Chapter ... [full story]

Configuring OSPF Configuring OSPF is a simple task. There are many options that are allowed within OSPF, such as statically configuring neighbors, creating a virtual link between an area that is not physically connected to Area 0, neighbor/adjacency encryption, and ... [full story]