IS-IS is similar to OSPF; it uses the default-information originate router subcommand. In the configuration for RTA in Example 12-59, RTA originates a default into IS-IS only on the condition that RTA learns the default from its exterior link. Example 12-59. Using IS-IS as the IGP: RTA Configuration router isis 100 redistribute connected default-information originate route-map SEND_DEFAULT_IF net 49.0001.0000.0c00.000a.00 router bgp 3 no synchronization network 172.16.220.0..
Triggered (Flash) Updates and Poisoned Routes
When RIP knows for sure that a route to a subnet has failed, RIPv2 can converge to an alternate route typically in less than a minute. Example 8-2 details the steps behind one such example, using Figure 8-1, with the steps outlined in the following list (the comments in Example 8-2 refer to these steps by number): 1. RIP debug messages show R1’s RIP updates, including R1’s use of split horizon. 2. R3’s E0/0 interface is shut down, simulating a failure. 3. R3 immedi..
So far in this chapter, most of the discussion has been about examining existing addresses and subnets. Before deploying new networks, or new parts of a network, you must give some thought to the ranges of IP addresses to be allocated. Also, when assigning subnets for different locations, you should assign the subnets with thought for how routes could then be summarized. This section covers some of the key concepts related to subnet allocation and summarization. (This s..
Link-state packets are divided into two types: level 1 and level 2. Level 2 packets contain information about all the reachable prefixes within the IS-IS domain. The topology for level 1 packets is known for the local area only, so these packets are included in the level 1 LSP. Individual LSPs are identified by four components of the LSP header. These include the LSP ID, the sequence number, the checksum, and the remaining lifetime. LSP ID is divided into the source ID, the P..
Using an Async Modem on the AUX Port
Many Cisco routers include an AUX port that is a low-speed asynchronous serial interface that can connect to a standard modem and support PPP: Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router2(config)#interface Async65 Router2(config-if)#encapsulation ppp Router2(config-if)#dialer in-band Router2(config-if)#dialer pool-member 1 Router2(config-if)#ppp authentication chap Router2(config-if)#async default routing Router2(conf..
