T1/E1 and Primary Rate Interfaces, T1s, and DS
Usage of T1s is still a growing LEC and inter-exchange carrier (IXC) service. The T1 signal can be transmitted one mile before requiring a repeater, which regenerates the signals, recovers the timing, and sends the regenerated version of the coding sequence. A T1 signal is referred to as a DSX-1 interface (digital signal crossconnection point for DS- 1 signals), which is capable of sending/receiving the T1 signal up to 655 feet. The maximum distance between the CSU and the l..
RIP Next-Hop Feature and Split Horizon
This section covers the split horizon and next-hop features of RIPv2. These two features do not typically need to be considered at the same time, but in some cases they do. The example used in this section shows how the two features may be needed in the same design. First, Cisco IOS controls the split horizon setting per interface, using the [no] ip split-horizon interface subcommand. Split horizon is on by default, except for cases in which Frame Relay is configured with the..
CIDR, Private Addresses, and NAT
The sky was falling in the early 1990s in that the commercialization of the Internet was rapidly depleting the IP Version 4 address space. Also, Internet routers’ routing tables were doubling annually (at least). Without some changes, the incredible growth of the Internet in the 1990s would have been stifled. To solve the problems associated with this rapid growth, several short-term solutions were created, as well as an ultimate long-term solution. The short-term solution..
When a router receives a CSNP from a neighbor, and it notices that the CSNP is missing part of the database, the router sends a partial sequence number PDU packet (PSNP) to request a newer copy of the LSP. This is similar to the OSPF link-state request packet. The PSNP also acknowledges the receipt of the CSNP. PSNP describes the LSP by its header, just like a CSNP. Unlike the CSNP, however, the PSNP holds information only about the requested LSP, not about all ..
Mitigating the Detrimental Effects of the IS-IS Restart
This section describes two different approaches to reduce the negative effects resulting from the original IS-IS restart behavior. The first approach, referred to as the IETF IS-IS restart mechanism, extends the IS-IS protocol and requires that both the restarting router and its neighbors (also known as helper nodes) be restart-capable.[4] As a result, for an adjacency when both neighbors are not IETF IS-IS restart-capable, the IS-IS restart behavior on that adjacency reverts..
