OSPFv3 also differs from OSPFv2 in many ways. The most obvious is that OSPFv3 supports 128-bit prefixes. OSPFv3 runs directly within IPv6 packets and can co-exist with OSPFv2. The two routing protocols do not exchange information or pay attention to each other in any way (this is referred to as "ships in the night" routing in some documentation, because packets from the two versions of OSPF pass each other without knowing of the other's existence, like ships passing in ..
Flooding on Broadcast Networks
Flooding is optimal over the broadcast network when the IS creates a pseudonode. For each pseudonode, a DIS is responsible for creating and updating the pseudonode LSP and for conducting the flooding over the LAN. Unlike OSPF, there is no backup DIS. The DIS sends CSNP every 10 seconds; the LSP is not acknowledged. If a router notices that part of its database is missing or that the entry in its database is old, it sends a PSNP requesting a newer copy of the LSP. ..
The IETF IS-IS restart mechanism extends the IS-IS protocol and requires that both the restarting router and its neighbors be able to support these capabilities. In contrast, the Cisco IS-IS restart mechanism does not make any externally observable protocol changes. That is, the IS-IS restart on a router is hidden from its neighbors. First, this mechanism requires transmission of IIH packets quickly following the restart before an adjacency's hold time expires. Second, to con..
Sometimes funny things happen when the primary link comes back and the backup link has not yet disconnected. These problems are usually due to poor routing metrics, causing at least one of the routers to prefer the dial path, even if the primary is available. The easiest way to handle these problems is to use bandwidth commands to ensure that the primary is the better path: Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router1..
Configuring the Frame Relay ELMI Feature
This section explains the configuration tasks required to configure Frame Relay QoS Autosense and Frame Relay Address Registration on Cisco devices. Practical configuration examples are used to illustrate the relevant Cisco IOS configuration commands. This section also introduces the related Cisco IOS show and debug commands for monitoring and maintaining Frame Relay ELMI configurations on a Cisco router. Configuring Frame Relay QoS Autosense This section discusses the Cisc..
