OSPFv3 and OSPFv2 use a similar set of LSAs, with some differences. Table 21-2 lists the OSPFv3 LSAs, including the LSA function code, which indicates the function of the LSA. Table 21-2. OSPFv3 LSAs Note The LSA link-state (LS) type is created by concatenating 0x200 with the LSA function code. For example, LSA function code 1 has an LS type 0x2001. LSA types 1 and 2 no longer contain route prefixes; instead, they contai..
Routers sharing a common data link layer become IS-IS neighbors if the Hello packets that they exchange meet the criteria for forming an adjacency. Although the process of finding a neighbor differs slightly depending on the media, the information sent in the Hellos is essentially the same. Each Hello states the originator of the Hello and the capabilities of its interface. If the Hellos are exchanged and the criteria are met, an adjacency is formed and the Integrated I..
Currently, IS-IS is being used as an IGP by some of the largest ISPs. In most cases, a well- defined ISP network should not have a large IGP routing table, but due to extensive redundancy, scaling does become a problem. In addition, even if the IGP has a strong addressing structure, sometimes it must find specific routes to the next hop according to strict policy requirements. For this reason, route summarization is not always possible. Experience in working wit..
IS-IS Multiple Area Configuration
This section uses the network in Figure 7-12 to investigate the properties of a multiple area IS-IS network. The loopback addresses, system IDs, and NSAP addresses for the routers in area 17 are listed in Table 7-3. Figure 7-12. Multiple Area IS-IS Network [View full size image] Table 7-3. Additional Loopback and System IDs for Figure 7-12 Router Loopback System ID NSAP F 172.16.17..
Table 6-3 illustrates that there are actually five STP states
After the bridges have classified their ports as Root, Designated, or non-Designated, creating a loop-free topology is straightforward: Root and Designated Ports forward traffic, whereas non-Designated Ports block traffic. Although Forwarding and Blocking are the only two states commonly seen in a stable network, Table 6-3 illustrates that there are actually five STP states. Table 6-3. STP States State Purpose Forwarding Sendin..
