Split Horizon, Routing update, Distance Vector, Poison Route, Periodic Update, Routing Table, metric, passive interface, auto summary

Split Horizon:

Split horizon is a method of preventing a routing loop in a network. The basic principle is simple: Information about the routing for a particular  packet is never sent back in the direction from which it was received.

Routing  Update:

A message defined by routing protocol  that lists routing information, including the subnet number, subnet mask, and metric.etc.

 

Distance Vector:

Distance Vector means that Routers are advertised as vector of distance and direction. 'Direction' is represented by next hop address and exit interface, whereas 'Distance' uses metrics such as hop count.

Routers using distance vector protocol do not have knowledge of the entire path to a destination. Instead Distance Vector uses two methods:

1. Direction in which or interface to which a packet should be forwarded.
2. Distance from its destination.

 

Poison Route:

A route listed in a routing update that the routing protocol purposefully assigns a metric value considered to be infinite, meaning that the route has failed.

Periodic Update:

A routing protocol behavior in which the routing protocol sends Update messages on a regular interval (the period).

 

Routing Table:

A list kept by routers that lists the best IP routes known to the router. Each entry lists a subnet or network, the associated mask, possibly the outgoing interface and/or IP address of the next-hop router, and other related info.

Metric :

A numeric value that a routing protocol uses to imply how good a particular route is, so that when a router learns more than 1 route for the same network/subnet, the router can choose the best route as the route with the lowest metric.

Passive Interface:

An interface local to a router, for which the routing protocol does not send routing protocol messages out to that interface. Different routing protocol has different view about Passive interface , in RIP  when passive interface command applied in a interface  , router will not send any update through  that interface however will receive update . in EIGRP if passive interface command applied router will not form any adjacency , because the command will not allow EIGRP hello .

 

Auto Summary:

If auto summary is enabled , router will automatically summary all routes in their class full boundaries .let say you have used a class B ip address 172.16.0.0/16 and subnet ed into many network ( 172.16.1.0/24  , 172.16.2.0/24 ) , however if auto summary is enable in your configuration ,  you will see only   one summary  route (172.16.0.0/16)  in your routing table .