Distance Vector Routing Protocols in Networking

Study Notes

Distance vector routing protocols use the best path to the destination if the distance to the destination is successively shorter.
Examples of distance vector routing protocols include IPX RIP and IP RIP.

Each router using distance vector routing begins by identifying its own neighbours.
The interface to each directly connected network is shown in the routing tables as having a distance of 0.
Routers discover the best path to destination networks based on accumulated metrics from each neighbour.

IPsec is a protocol for IP network-layer encryption and authentication.
It is an integral part of the base protocol suite in IPv6.
IPsec is not widely deployed except for securing traffic between IPv6 BGP routers.

Mobile IPv6 (MIPv6) avoids triangular routing and is therefore as efficient as normal IPv6.
Neither MIP nor MIPv6 are widely deployed today.

IPv6 addresses are 128 bits long, whereas IPv4 addresses are 32 bits.
IPv6 has enough room for 3.4×10^38 unique addresses.
IPv6 addresses are typically composed of two logical parts: a 64-bit (sub-)network prefix, and a 64-bit host part.

The RXBoot image (also known as Bootloader) is a "cut-down" version of the IOS located in the router's ROM.
The RXBoot image allows for minor maintenance operations and brings various interfaces up or down.
The RAM is where the router loads the IOS and the configuration file.
The NVRAM (Non-Volatile RAM) is a special memory place where the router holds its configuration.
The ROM is used to start and maintain the router.

RIP is a distance vector protocol that measures the distance to reach a remote network by calculating hop count.
The RIP metric calculates the number of routers that a packet has to pass through from its source router to reach the destination network.
RIP uses the Bellman Ford algorithm to find the best route.
Characteristics of RIP include:
- It is an IGP Interior Gateway Protocol – works within AS
- Administrative distance of RIP is 120
- Supports classless routing and VLSM (RIPv2)
- Uses metric – HOP COUNT to decide best path to reach a destination
- Sends periodic update messages to next RIP routers
- Entire routing table is sent each time
- Maximum number of hops supported by RIP is 15
- A route with Hop count 16 is considered as an invalid route
- A RIP update message carries a maximum of 25 routes
- RIP uses UDP as transport layer and identified by port no 520
- For avoiding routing loops RIP uses the following mechanisms:
  - Split horizon
  - Route poison