Routing

 View Only

IMPORTANT MODERATION NOTICE

This community is currently under full moderation, meaning  all posts will be reviewed before appearing in the community. Please expect a brief delay—there is no need to post multiple times. If your post is rejected, you'll receive an email outlining the reason(s). We've implemented full moderation to control spam. Thank you for your patience and participation.



  • 1.  BGP route selection question

    Posted 21 days ago
    If the routing table has a prefix learned from bpg neighbor and via instance-import, the bgp selection rules are still the same.
    Any possibility for the following next-hop selected (192.168.0.45) to switch to 192.168.0.57 ?
    run show route table CE2-1.inet.0 192.168.0.88/30 extensive    
    
    CE2-1.inet.0: 41 destinations, 55 routes (41 active, 0 holddown, 0 hidden)
    192.168.0.88/30 (2 entries, 1 announced)
    TSI:
    KRT in-kernel 192.168.0.88/30 -> {192.168.0.45}
    Page 0 idx 1, (group ebgp type External) Type 1 val 0xdca4834 (adv_entry)
       Advertised metrics:
         Nexthop: Self
         AS path: [64600] 54591 I
         Communities: target:54591:201
    Path 192.168.0.88 from 192.168.0.45 Vector len 4.  Val: 1
            *BGP    Preference: 170/-101
                    Next hop type: Router, Next hop index: 1559
                    Address: 0xdee8bf0
                    Next-hop reference count: 41
                    Source: 192.168.0.45
                    Next hop: 192.168.0.45 via ge-0/0/0.312, selected
                    Session Id: 0x1ad
                    State: <Active Ext>
                    Local AS: 64600 Peer AS: 54591
                    Age: 1:15:09 
                    Validation State: unverified 
                    Task: BGP_54591_64600.192.168.0.45
                    Announcement bits (3): 1-KRT 2-rt-export 3-BGP_RT_Background 
                    AS path: 54591 I 
                    Communities: target:54591:201
                    Accepted
                    Localpref: 100
                    Router ID: 172.30.5.10
             BGP    Preference: 170/-101
                    Next hop type: Router, Next hop index: 1571
                    Address: 0xeb08830
                    Next-hop reference count: 44
                    Source: 192.168.0.57
                    Next hop: 192.168.0.57 via ge-0/0/0.315, selected
                    Session Id: 0x1bf
                    State: <Secondary NotBest Ext>
                    Inactive reason: Not Best in its group - Active preferred
                    Local AS: 64600 Peer AS: 54591
                    Age: 5:37 
                    Validation State: unverified 
                    Task: BGP_54591_64600.192.168.0.57
                    AS path: 54591 I 
                    Communities: target:54591:201
                    Accepted
                    Localpref: 100
                    Router ID: 172.30.5.14
                    Primary Routing Table CE2-2.inet.0
    
    [edit]
    ​
    thanks a lot !!



  • 2.  RE: BGP route selection question
    Best Answer

     
    Posted 19 days ago
    The two routes seem to have all the same base criteria and it is simply selecting the oldest one in the table right now.

    If you want to insure that one of the routes is always preferred then you would need to adjust the import policy on one of the peers.  Typically either lowering or raising the local preference value by that peer as needed.  This would insure the routes are used in the desired order at all times.

    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP - Retired)
    http://puluka.com/home
    ------------------------------



  • 3.  RE: BGP route selection question

    Posted 19 days ago
    thanks a lot !!