Information Technology Reference
In-Depth Information
administrative distance of 90 and OSPF has an administrative distance of 110, the router
enters the EIGRP route in the routing table and sends packets with destinations of
172.20.10.0/24 out Ethernet 0.
Static routes have a default administrative distance of 1. There is one exception. If the
static route points to a connected interface, it inherits the administrative distance of con-
nected interfaces, which is 0. You can configure static routes with a different distance by
appending the distance value to the end of the command.
Ta ble 1 0 - 6 provides a summary of routing protocol characteristics.
Ta b l e 1 0 - 6
Routing Protocol Characteristics
Routing
Protocol
Distance Vector or
Link State
Interior or
Exterior
Classful or
Classless
Administrative
Distance
RIPv2
DV
Interior
Classless
120
EIGRP
DV (hybrid)
Interior
Classless
90
OSPF
LS
Interior
Classless
110
IS-IS
LS
Interior
Classless
115
BGP
Path vector
Both
Classless
20
Routing protocols use a metric to determine best routes to a destination. Some routing
protocols use a combination of metrics to build a composite metric for best path selec-
tion. This section describes metrics and also covers routing loop-prevention techniques.
Yo u m u s t u n d e r s t a n d e a c h m e t r i c fo r t h e C C DA .
Some routing metric parameters are
Hop count
■
Bandwidth
■
Cost
■
Load
■
Delay
■
Reliability
■
Maximum transmission unit (MTU)
■
Hop Count
The hop count parameter counts the number of links between routers the packet must tra-
verse to reach a destination. The RIP routing protocol uses hop count as the metric for
problem with routing protocols that use only this metric is that the shortest hop count is
