A 6-to-4 tunnel works similarly to a manual tunnel, except that the tunnel is set up automatically. 6-to-4 tunnels use IPv6 addresses that concatenate 2002::/16 with the 32- bit IPv4 address of the edge router, creating a 48-bit prefix. An example of 6-to-4 tunneling is shown in Figure 21-5. The tunnel interface on Router A has an IPv6 prefix of 2002:C0A8:501::/48, where C0A8:501 is the hexadecimal equivalent of 192.168.5.1, the IPv4 address of its interface in the IP..
The show isis spf-log command explains a great deal about the SPF calculations on the router. It reveals the events that triggered SPF for the last 20 occurrences. To display how often, and why, the router has run a full SPF calculation, use the show isis spf-log EXEC command. Example 10-13 shows output for the show isis spf-log command. The example shows that Router A sent an LSP because it had set the ATT bit, and later it generated a new LSP when new adjacenc..
Establishing Adjacencies on an NBMA Link
The creation and maintenance of adjacencies becomes more complicated when used over non-broadcast links. An NBMA link is neither a broadcast medium nor a point-to-point link; it is a little of both. Furthermore, IS-IS does not have an NBMA link type. Using PVCs, NBMAs provide multiple connections, which could be viewed as a LAN. The confusion occurs when Integrated IS-IS sees the link is multiaccess. Having no knowledge of multiaccess WAN clouds, Integrated IS-IS believes tha..
The behavior of link-state protocols is different when handling non-broadcast multiaccess networks. In this situation, a difference always exists between physical and logical topology. For broadcast networks, for example, a pseudonode is created and is flooded with the ID set to the ID of the DIS. The broadcast model will also be successful in the frame or ATM cloud, as long as all the virtual circuits are operating properly. When a PVC breaks down, forwarding and routing is ..
Migrating Token Ring to Ethernet
Many Token Ring users contemplate a migration from Token Ring to Ethernet. In some cases, the motivation is the available bandwidth of Fast Ethernet. Sometimes the motivation is to simplify cabling. But moving an infrastructure from Token Ring to Ethernet involves several considerations. For example, the media cabling type might differ. Many Token Ring systems utilize Category 3 cable (shielded twisted-pair), whereas Ethernet typically uses Category 5 cable (unshielded twiste..
