relative to OSPF, IS-IS is included in Link-State Advertisement (鏈路狀態通告)
IS-IS is ISO Dynamic Routing Spec, it is a link-state routing protocol that floods link-state info building topology thru network.
It can route IP packets and route CNLP, conectionless network protocol packets. IS-IS is deemed to be an alternative to OSPF and EIGRP.
It is commonly used in ISP network, but merely to be seen in Enterprise network.
It uses a metric wiht a max path value of 1024. It is intended to measure the capacity of circuit of traffic, such as it thruput in bps.
Higer Value indicates Lower Capacity.
Any single link can have a max value of 64. IS-IS calculates path values by sum up links values. In this way, it helps to check the shortest-path algorithm is executed effectively and its metrics provide the granularity to support diversified link types.
Their interface's default metric is 10. Thus Administrator shall config the value.
Small Value proofs insufficient to Large Network(High Bandwidth)
This is why Cisco uses "wide metrics" instead now. It provides Link Value with max val of 2e24, and total path metric of 2e32.
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