Security Benefits of Network Address Translation
NAT used in PAT mode can be a source of security for the network that is using PAT to translate its private addresses. To understand this, assume that the device doing the NAT is a router that is sitting on the edge of the network, with one interface connected to the RFC 1918 private network and another interface connected to the Internet. When a device sitting behind the router wants to go out to the Internet, it sends packets to the router. The router then translates the s..
Matching COMMUNITY with Community Lists
Cisco originally created communities as a proprietary feature, treating the 32-bit COMMUNITY as a decimal value (as shown in Example 13-11). When the COMMUNITY PA was added to the BGP standard RFC 1997, the 32-bit COMMUNITY was formatted as AA:NN, where AA is a 16- bit number to potentially represent an ASN, and NN represents a value as set by that ASN. However, the COMMUNITY PA remained a 32-bit number. Cisco routers can use either the original format or the RFC 1997 forma..
OSPF Path Selection Between Areas
The local routing table on a router depends on its position in the network and the type of area it is in. If there are routes with different routing information sources to the same destination, the router chooses the path with the lowest administrative distance. If both are OSPF, OSPF will select lower type advertisements first and choose lower costs to break ties. OSPF, like all IP routing protocols on Cisco IOS, is capable of load-balancing and will automatically distribute..
This section introduces the structure of the IP address, including the network, subnetwork, and host portions. We explain how a user determines what IP addressing to use and what configuration commands are required to implement the desired address scheme. Address Structure TCP/IP is a collection of communication protocols that define how different computers are addressed on the network, what methods are used to move information from one computer to another, and some service..
Providing a Backup to Frame Relay Virtual Circuits
Using secondary connections to back up the main Frame Relay virtual circuits allows organizations to continue their business operations by ensuring network connectivity in the event of failures to the primary connections. Provisioning a secondary backup connection to the primary Frame Relay virtual circuit can prevent a single point of failure in the network. Some Frame Relay carriers offer network redundancy services by provisioning a secondary virtual circuit as a backup t..
