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independent-domain what is the use of it

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  • 1.  independent-domain what is the use of it

    Posted 04-06-2011 21:38

    Hi Expert

     

    Can any one explain to me what is the use of “ independent-domain “  under the  routing-instances , and please give me an example of when i should use it  

     

    Many Thanks



  • 2.  RE: independent-domain what is the use of it
    Best Answer

     
    Posted 04-08-2011 00:17

    Hi,

        Basically we would use "independet-domain", when the customer route attributes has to be transparently fowarded across the VPN network
    even without having the service-provider AS path in the routes.

    Let's say we have a netwoek like this:


                    |<-----VPN-------->|
          
    internal                                                                 internal
    routes   +-----+          +-----+            +-----+           +-----+   routes
    ======>  | CE1 |----------| PE1 |************| PE2 |-----------| CE2 |  <========
             +-----+          +-----+            +-----+           +-----+

                 |<---EBGP------>|                    |<---EBGP------>|

    If the administrator of customer site wants to make routing decisions based on their own route attributes,
    then with VPN network (without "independet-domain") would not help.

    Say on CE1, we have a internal route as below,


    suryak@CE1# run show route protocol bgp 110.1.1.1/32 detail

    inet.0: 40 destinations, 40 routes (39 active, 0 holddown, 1 hidden)
    110.1.1.1/32 (1 entry, 1 announced)
            *BGP    Preference: 170/-101
                    Next hop type: Indirect
                    Next-hop reference count: 3
                    Source: 200.10.0.1
                    Next hop type: Router, Next hop index: 547
                    Next hop: 200.10.0.1 via ge-5/1/0.0, selected
                    Protocol next hop: 200.20.0.1
                    Indirect next hop: 8e23240 1048574
                    State: <Active Int Ext>
                    Local AS:   100 Peer AS:   100
                    Age: 1  Metric: 10      Metric2: 2
                    Task: BGP_100.200.10.0.1+179
                    Announcement bits (3): 0-KRT 4-BGP RT Background 5-Resolve tree 1
                    AS path: I (Originator) Cluster list:  33.33.33.33
                    AS path:  Originator ID: 10.255.178.60
                    Accepted
                    Localpref: 100
                    Router ID: 200.10.0.1


    When the same is advertised across the VPN network to CE2, it appreas as


    suryak@CE2# run show route protocol bgp 110.1.1.1/32 detail

    inet.0: 35 destinations, 35 routes (34 active, 0 holddown, 1 hidden)
    110.1.1.1/32 (1 entry, 1 announced)
            *BGP    Preference: 170/-101
                    Next hop type: Router, Next hop index: 513
                    Next-hop reference count: 4
                    Source: 20.0.0.1
                    Next hop: 20.0.0.1 via ge-3/1/1.0, selected
                    State: <Active Ext>
                    Local AS:   100 Peer AS:   200
                    Age: 36:40
                    Task: BGP_200.20.0.0.1+179
                    Announcement bits (1): 0-KRT
                    AS path: 200 200 I
                    Communities: target:100:100
                    Accepted
                    Localpref: 100
                    Router ID: 20.0.0.1



    If we analyse the customer route attributes like  Originator ID, Cluster list, Metric, AS path are not transparent from CE1 to CE2.


    In this case we like to have a transprancy for route attribute, then we can use "independet-domain".


                    |<-----VPN-------->|
          
    internal                                                                 internal
    routes   +-----+          +-----+            +-----+           +-----+   routes
    ======>  | CE1 |----------| PE1 |************| PE2 |-----------| CE2 |  <========
             +-----+          +-----+            +-----+           +-----+

                 |<---IBGP------>|                    |<---IBGP------>|



    Taking the same route on CE1, we can see the difference.

    suryak@CE1# run show route protocol bgp 110.1.1.1/32 detail            

    inet.0: 40 destinations, 40 routes (39 active, 0 holddown, 1 hidden)
    110.1.1.1/32 (1 entry, 1 announced)
            *BGP    Preference: 170/-101
                    Next hop type: Indirect
                    Next-hop reference count: 3
                    Source: 200.10.0.1
                    Next hop type: Router, Next hop index: 547
                    Next hop: 200.10.0.1 via ge-5/1/0.0, selected
                    Protocol next hop: 200.20.0.1
                    Indirect next hop: 8e23240 1048574
                    State: <Active Int Ext>
                    Local AS:   100 Peer AS:   100
                    Age: 5:31       Metric: 10      Metric2: 2
                    Task: BGP_100.200.10.0.1+179
                    Announcement bits (3): 0-KRT 4-BGP RT Background 5-Resolve tree 1
                    AS path: I (Originator) Cluster list:  33.33.33.33
                    AS path:  Originator ID: 10.255.178.60
                    Accepted
                    Localpref: 100
                    Router ID: 200.10.0.1



    suryak@CE2# run show route protocol bgp 110.1.1.1/32 detail             

    inet.0: 35 destinations, 35 routes (34 active, 0 holddown, 1 hidden)
    110.1.1.1/32 (1 entry, 1 announced)
            *BGP    Preference: 170/-101
                    Next hop type: Indirect
                    Next-hop reference count: 6
                    Source: 20.0.0.1
                    Next hop type: Router, Next hop index: 513
                    Next hop: 20.0.0.1 via ge-3/1/1.0, selected
                    Protocol next hop: 20.0.0.1
                    Indirect next hop: 91740e4 2097150
                    State: <Active Int Ext>
                    Local AS:   100 Peer AS:   100
                    Age: 18         Metric: 20      Metric2: 0
                    Task: BGP_100.20.0.0.1+179
                    Announcement bits (2): 0-KRT 3-Resolve tree 1
                    AS path: I (Originator) Cluster list:  33.33.33.33
                    AS path:  Originator ID: 10.255.178.60
                    Accepted
                    Localpref: 100
                    Router ID: 20.0.0.1



  • 3.  RE: independent-domain what is the use of it

    Posted 04-08-2011 10:34

    Thanks a lot   it's clear now  Smiley Happy



  • 4.  RE: independent-domain what is the use of it

     
    Posted 10-06-2013 23:36

    Hi Surya,

    So you're saying that PE1 receives a VPN route over its iBGP session with PE2, which it further advertises over its iBGP session with CE1. Is that possible without some sort of route reflection?



  • 5.  RE: independent-domain what is the use of it

     
    Posted 06-11-2017 18:29

    Old thread, but yes - re-advertising BGP routes from PE to CE using IBGP (even routes that were learnt via IBGP on a remote PE) is allowed, without configuring route-reflection.

     

    You should exercise caution when you have redundant PE links though (to the same or redundant VRF) as it becomes very easy to form a loop between two sites.  Without a cluster-id being added to the prefix somewhere along the line, there is nothing to stop it being re-distributed indefinitely.