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Overally it was quite well described in the book, therefore only the two things are so far incomprehensible for me.

1) What does IoO mean?
2) Could you explain these strange floating-point numbers that I've circled?

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up vote 1 down vote accepted

Lo0 refers to a local network in this case, though more correctly, lo0 refers to loopback networks. The numbers you have . so-0/0/x and the decimal numbers seems to be the addressing scheme sonet uses but I'm having trouble finding the RFC for that.

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lo0 (it's 0, not O) is shortened loopback 0 - kind of virtual interface used mainly in routing and management. Those numbers are just last octets for p2p links as described in left bottom corner:

Note: all links use 10.0.x.y, only last octets are shown

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lo0 is short for loopback 0, that is a virtual interface on the router (a device that connects two or more different networks). lo0 x.x.x.x, where x.x.x.x is the IP address of that virtual interface. x.x.x.x can be used for routing and/or management of that box, the router.

the circled numbers are IP addresses for the interfaces on the routers, physical interfaces. these IP addresses are used in routing and can be used for management as well.

additional note: lo0 interface is preferred for management since it does not go down, it is virtual, where the physical interface can go down, let us say if someone unplug the cable from the interface, it can't be reached anymore. where the lo0 can be reached if there is any other route to that devices.

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