Different ISPs offer different services, depending on how big they are and the infrastructure of their networks. Mainly, providers can be categorized by their method of physical Internet access, the applications they provide to customers, and the security services they provide. The following sections cover the service models that are most common throughout the Internet service provider market today. As you'll see, these services range from providing dial-up access via a telep..
Hellos, Neighbors, and Adjacencies
After a router has been configured for EIGRP, and its interfaces come up, it attempts to find neighbors by sending EIGRP Hellos (destination 224.0.0.10). Once a pair of routers have heard each other say Hello, they become adjacent—assuming several key conditions are met. Once neighbors pass the checks in the following list, they are considered to be adjacent. At that point, they can exchange routes and are listed in the output of the show ip eigrp neighbor command. ■ Mus..
Troubleshooting EIGRP Neighbor Relationships
This section discusses methods of troubleshooting issues regarding EIGRP neighbor relationships. The following are the most common causes of problems with EIGRP neighbor relationships: • Unidirectional link • Uncommon subnet, primary, and secondary address mismatch • Mismatched masks • K value mismatches • Mismatched AS numbers • Stuck in active • Layer 2 problem • Access list denying multicast packets • ..
Besides supporting the Easy VPN Server function, certain routers also can be Easy VPN Remotes. These routers include the 800, ubr900, and 1700 series routers. This was introduced in IOS 12.2(4)YA and 12.2(13)T. As you saw in the last section, setting up an Easy VPN Server on a router from the CLI is not the simplest process in the world. Because of this complication and because administrators at remote offices might not be very Cisco-savvy at configuring IPsec sessions, Cisco..
Prepending ASNs to the AS Path
As we mentioned in that recipe, that only affects your outbound path. If you also want to ensure that inbound traffic prefers one path over another, then you have to somehow trick the remote networks into believing that one path is better than the other. As we mentioned in the Introduction to this chapter, if there are many options for different paths to a destination network, a BGP router will go through several steps to decide which one to use. You can adjust the attribute..
