1

In my Juniper MX480, the logic-systems config is below:

[edit]
logical-systems {
    r1 {
        interfaces {
            ge-0/0/0 {
                unit 0 {
                    family inet {
                        address 10.1.1.1/24;
                    }
                }
            }
        }
    }                                   
    r2 {
        interfaces {
            ge-0/0/1 {
                unit 0 {
                    family inet {
                        address 10.1.1.2/24;
                    }
                }
            }
        }
    }
}

I have several questions about logic-systems:

1.whether I can regard the mx480 as two independent routers?
2.but you know they're only one config file(I am editing), whether the r1 and r2 use the same config file? if is, why they're set two instances, use one and use two they are take same function?

0
2

whether I can regard the mx480 as two independent routers?

Yes, these can be considered as two logical routers.

The Routing Protocol Daemon (RPD) typically runs a single instance for all protocols. Each logical-system creates its own instance of RPD in addition to the default.

See next answer for more details.

but you know they're only one config file(I am editing), whether the r1 and r2 use the same config file? if is, why they're set two instances, use one and use two they are take same function?

Technically speaking, yes, it's one configuration file. However, there are a couple ways to manage it.

You as the main user are currently operate the CLI from the global view, so you see everything. However, you can set the CLI to only use a particular logical-system and therefore expose only the relevant parts with the set cli logical-system command (operational mode, not configuration mode) and it'll drop you into a logical system specific prompt for easier configuration and operation.

root@HOST1> set cli logical-system LSYS1
Logical system: LSYS1

root@HOST1:LSYS1> show configuration
interfaces {
    lo0 {
        unit 1 {
            family inet {
                address 11.11.11.11/32;
            }
        }
    }
}
protocols {
    ospf {
        area 0.0.0.1 {
            interface lo0.1 {
                passive;
            }
        }
    }
}

root@HOST1:LSYS1> clear cli logical-system
Cleared default logical system

root@HOST1>

There are some limitations, for example someone who can operate the default logical system has to assign certain items (like interfaces) to the logical systems. Someone who can operate only that particular logical system, can do whatever they wish with the resources they have been assigned.

As one final example, the following configurations will achieve the same result. Again, notice the prompts.

Option 1

root@HOST1# set logical-systems LSYS2 protocols ospf area 2 interface lo0.2 passive

Option 2

root@HOST1> set cli logical-system LSYS2
Logical system: LSYS2

root@HOST1:LSYS2> configure
Entering configuration mode

[edit]
root@HOST1:LSYS2# set protocols ospf area 2 interface lo0.2 passive
0

Different logical-systems on a single Juniper system pretty much work like separate routers: addressing, routing, policies, ... are all separate. As you've noted, there's a single config though.

4
  • they use one config file, so the addressing, routing, policies, ... are the same, so what's the better versus one logical system? – aircraft Apr 8 at 9:16
  • The benefit is that you can run independent addressing and routing within each logical system - in case there are ambiguities, multiple clients with colliding addresses, ... – Zac67 Apr 8 at 9:25
  • I still don't understand, please explain more. – aircraft Apr 8 at 9:31
  • 1
    @aircraft it's not about logical systems being better, it's about whether or not you need to use them. Many folks use them for labs, instead of building 10 routers, you can build 10 logical-systems. That's just one example. – Jordan Head Apr 8 at 14:40

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