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  • Hirofumi Takahashi thinks this is interesting:

Reliability is measured dynamically and is expressed as an eight-bit number, where 255 is a 100 percent reliable link and 1 is a minimally reliable link. In the output of show interface, reliability is shown as a fraction of 255, for example, 234/255 (see Example 7-3).

From

Cover of Routing TCP/IP, Volume 1, 2/e

Note

Reliability is dynamically measured