Information Technology Reference
In-Depth Information
For Ethernet, calculate the cost as follows:
10
6
= 10
7
Cost (Ethernet) = 10
8
/ 10
7
= 10
BW = 10 Mbps = 10
×
The sum of all the costs to reach a destination is the metric for that route. The lowest cost is the
preferred path.
Load
The load metric refers to the degree to which the interface link is busy. The router keeps track
of the interface utilization. Routing protocols can use this metric in the calculation of a best
route. If you have 512 k and 256 k links to reach a destination, but the 512 k circuit is 99 percent
busy, and the 256 k is only 5 percent busy, the 256 k link is the preferred path. The load can be
verified with the
show interface
command. Lower load numbers are better. Example 2-1 shows
that the load is 1/255.
show interface
Command Used to Check the Current Load of the Interface
Example 2-1
router3>show interface serial 1
Serial1 is up, line protocol is up
Hardware is PQUICC Serial
Internet address is 10.100.1.1/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
load 1/255
Delay
The delay metric refers to the length in time to move a packet to the destination. Delay depends
on many factors, such as link bandwidth, utilization, port queues, and physical distance
traveled. The delay of an interface can be configured with the
delay
tens-of-microseconds
command, where
tens-of-microseconds
specifies the delay in tens of microseconds for an
interface or network segment. Example 2-2 shows that the delay of the interface is 20000
microseconds.
show interface
Command to Check the Delay of an Interface
Example 2-2
router3>show interface serial 1
Serial1 is up, line protocol is up
Hardware is PQUICC Serial
Internet address is 10.100.1.1/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
DLY 20000 usec
load 1/255
Reliability
The reliability metric is the dependability of a network link. There might be WAN links that
tend to go up and down throughout the day. These links receive a small reliability rating.
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