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..
Steady-State Operation by Continuing to Send Joins
To maintain the forwarding state of interfaces, PIM-SM routers must send PIM Join messages periodically. If a router fails to send Joins periodically, PIM-SM moves interfaces back to a pruned state. PIM-SM routers choose to maintain the forwarding state on links based on two general criteria: ■ A downstream router continues to send PIM joins for the group. ■ A locally connected host still responds to IGMP Query messages with IGMP Report messages for the group. Figure 20..
The Cisco PIX and ASA VPN capabilities have their roots in Cisco IOS VPN technologies. VPNs were first introduced in the Cisco IOS router product line and then added to the PIXs in an early 5.x release. Like the routers and the concentrators, Cisco PIXs support many VPN solutions including IPsec, PPTP, and L2TP. Because of their flexibility, they can be used in many different situations. The ASA was introduced in the spring of 2005. The ASA is a unique hybrid security applian..
The Cisco Intrusion Detection System (IDS) provides an in-depth, self-healing mechanism to provide network administrators a defense against attacks from inside and outside the network. The Cisco definition of a self-healing network is a network that is intelligent enough to stop unwanted traffic and correct any security vulnerabilities before they occur. Beginning with Cisco IDS 4.0, the network IDS sensors use the Remote Data Exchange Protocol (RDEP) for communication. With..
if you don't configure a valid DNS nameserver, the router sends these queries to the local broadcast IP address, 255.255.255.255. Querying a nonexistent nameserver is not only unproductive, but it can also be quite time consuming if it happens in an interactive session, since the router will not return the EXEC prompt until the query times out. This can be quite frustrating because, by default, the router will interpret any unknown command as a hostname that you want to conne..
