Routing

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Can anyone help to understand what the following line is for ?

  • 1.  Can anyone help to understand what the following line is for ?

    Posted 05-05-2021 23:32
    I came across a sample configuration for the following topology

    Area 2 is a discontinuous area. So a GRE is used to connect Area 2 to area 0 with R1 as ABR
    The configuration on R3 as follows:
    set interfaces ge-0/0/1 unit 0 family inet address 32.1.10.1/30
    set interfaces ge-0/0/2 unit 0 family inet address 32.2.10.1/30
    set interfaces gr-0/0/10 unit 0 tunnel source 3.3.3.3
    set interfaces gr-0/0/10 unit 0 tunnel destination 1.1.1.1
    set interfaces gr-0/0/10 unit 0 family inet address 172.16.1.3/24
    set interfaces lo0 unit 0 family inet address 3.3.3.3/32
    set routing-options static route 1.1.1.1/32 next-hop 32.1.10.2
    set protocols ospf area 0.0.0.1 area-range 3.3.3.3/32 restrict
    set protocols ospf area 0.0.0.1 area-range 32.0.0.0/8
    set protocols ospf area 0.0.0.1 interface lo0.0 passive
    set protocols ospf area 0.0.0.1 interface ge-0/0/1.0 interface-type p2p
    set protocols ospf area 0.0.0.2 interface ge-0/0/2.0 interface-type p2p
    set protocols ospf area 0.0.0.2 interface gr-0/0/10.0
    ​

    I do not understand the following line
    set protocols ospf area 0.0.0.1 area-range 3.3.3.3/32 restrict

    The explanation says the gre tunnel source address should not be advertised into Area 1, otherwise suboptimal routing could occur.

    Anyone can coach me what this line for ?

    thanks a lot !!



  • 2.  RE: Can anyone help to understand what the following line is for ?

    Posted 05-08-2021 11:36

    area-range is used for summarization and controlling routes between two areas, on ABR. please see below resources from Juniper.

    (Area border routers only) For an area, summarize a range of IP addresses when sending summary link advertisements (within an area). To summarize multiple ranges, include multiple 
    area-range statements.

    https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/ref/statement/area-range-edit-protocols-ospf.html

    here is an example that might help you understand:
    https://www.juniper.net/documentation/en_US/junos/topics/example/ospf-route-summarization-configuring.html




  • 3.  RE: Can anyone help to understand what the following line is for ?

    Posted 05-08-2021 11:47
    thanks a lot !!

    What I do not fully understand from the explanation above is "set protocols ospf area 0.0.0.1 area-range 3.3.3.3/32 restrict".  
    1.  I thought the loopback IPs are advertised via ospf for them to be reachable to each other for GRE establishment. The restrict aims to stop it advertised. I do know why.
    2.  I tested and did not find any difference whether I used this line or not. area-range is normally used on ABR connected to backbone area.