Interface Troubleshooting

Interfaces can have a variety of issues depending on the actual interface type, and listing all the possibilities would require a separate book! Instead, in this section, we will discuss a few common issues that illustrate the types of troubleshooting commands available on the router.

Address Configuration Issues

Since Juniper Networks routers allow multiple IP addresses to be configured on a single logical unit, configuration errors can occur if care is not taken. Lager has an IP address of 10.10.20.122 configured on its fast Ethernet interface with a subnet mask of /24. This was noticed to be a configuration error as the mask should have been configured for /27.

[edit interfaces fe-2/0/1]
root@Lager#show
vlan-tagging;
unit 100 {
    vlan-id 100;
    family inet {
        address 10.10.20.122/24;
    }
}

Here, the address of 10.10.20.122 is added with the correct subnet of /27:

[edit interfaces fe-2/0/1]
root@Lager#set unit 100 family inet address 10.10.20.122/27

When you view the resultant interface configuration the router appears to contain the duplicate IP addresses with varying subnet masks. This illustrates the fact that IP addresses are not overridden per logical unit, but simply are added to the logical unit.

[edit interfaces fe-2/0/1]
root@Lager#show
vlan-tagging;
unit 100 {
    vlan-id 100;
    family inet {
        address 10.10.20.122/24;
        address 10.10.20.122/27;
    }
}

To correct this, the old address with the /24 mask is removed by use of the delete command:

[edit interfaces fe-2/0/1] ...

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