What is the default metric for IS-IS interfaces?
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A. B. C. D.B
The protocol IS-IS does have an ability to use reference bandwidth to dynamically calculate link costs, but the default behavior has a value of 10 assigned to all transit interfaces.
IS-IS (Intermediate System to Intermediate System) is a routing protocol that is widely used in large-scale networks. When configuring IS-IS, one of the important considerations is the metric that is assigned to each interface.
The metric is used to determine the best path to a destination network. The lower the metric value, the better the path. The default metric value for IS-IS interfaces varies depending on the link type.
For point-to-point links, such as serial links, the default metric value is 10. This means that a direct connection between two routers is considered a better path than a connection with a metric value of 11 or higher.
For LAN interfaces, such as Ethernet interfaces, the default metric value is based on the bandwidth of the interface. The formula for calculating the default metric value for a LAN interface is:
metric = reference bandwidth / interface bandwidth
The reference bandwidth is a configurable value that is set to 10^8 (100 Mbps) by default. So, for example, if the interface bandwidth is 1 Gbps, the default metric value would be 100 / 1000 = 0.1.
It is important to note that the default metric value is only used if a specific metric value is not configured for an interface. In most cases, it is recommended to configure the metric value manually to ensure optimal routing.