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  • 1.  Need a urgent help regarding route manipulation

    Posted 06-12-2024 18:46

    Hi Guys  , Hope you guys are doing well , so my problem is i am trying to do a route manipulation in a customer network, So i have 3 ISPs  .
    ISP1- 10.10.10.1 , int-ge-0/0/0
    ISP2-20.20.20.1, int-ge-0/0/1
    ISP3-30.30.30.1, int - ge-0/0/2
    LAN1 - 192.168.0.1/24 , int -0/0/3
    LAN2-172.16.0.1/24 ,int-0/0/4
    All the isps are connected via  eBGP.
    Now my preferences are :
    172.16.0.1 - ISP3>ISP2>ISP1
    192.168.0.1- ISP2>ISP3>ISP1
    i am using as-path-prepand on export policy , it is taking the right interface (ge-0/0/2) but in trace route it is showing ISP2's IP as next hop.
    root# run ping 8.8.8.8 source 172.16.0.1 detail 
    PING 8.8.8.8 (8.8.8.8): 56 data bytes
    64 bytes from 8.8.8.8 via ge-0/0/2.0: icmp_seq=0 ttl=254 time=313.298 ms
    64 bytes from 8.8.8.8 via ge-0/0/2.0: icmp_seq=1 ttl=254 time=83.119 ms
    64 bytes from 8.8.8.8 via ge-0/0/2.0: icmp_seq=2 ttl=254 time=81.077 ms
    64 bytes from 8.8.8.8 via ge-0/0/2.0: icmp_seq=3 ttl=254 time=14.460 ms
    64 bytes from 8.8.8.8 via ge-0/0/2.0: icmp_seq=4 ttl=254 time=127.108 ms
    64 bytes from 8.8.8.8 via ge-0/0/2.0: icmp_seq=5 ttl=254 time=217.713 ms
    ^C
    --- 8.8.8.8 ping statistics ---
    6 packets transmitted, 6 packets received, 0% packet loss
    round-trip min/avg/max/stddev = 14.460/139.463/313.298/98.914 ms

    [edit]
    root# run traceroute 8.8.8.8 source 172.16.0.1     
    traceroute to 8.8.8.8 (8.8.8.8) from 172.16.0.1, 30 hops max, 52 byte packets
     1  20.20.20.1 (20.20.20.1)  521.520 ms  519.456 ms  44.076 ms
     2  192.168.25.2 (192.168.25.2)  238.321 ms *  63.903 ms

    [edit]
    root# 

    Can you guys please help me with it ? 



    ------------------------------
    DEBTANU BISWAS
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  • 2.  RE: Need a urgent help regarding route manipulation

    Posted 06-13-2024 10:23

    as-path prend on export policy -> does something for incoming traffic.

    Nothing to do with outgoing traffic (your traceroute). Have a look at your import policies and set local-pref.



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    Olivier Benghozi
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  • 3.  RE: Need a urgent help regarding route manipulation

    Posted 06-17-2024 06:55

    Indeed, as already mentioned, as-path-prepend is to (possibly) control traffic, ENTERING your ASN.

    To manipulate exit point FROM your ASN, try to set highest localpref for the needed neighbor.

    Worth mentioning that in case you set highest localpref for default or specific route towards one of BGP peers, it will not differentiate exit point based on the traffic source. Filter-based-forwarding (aka PBR - policy-based-routing) can solve this problem to override regular routing.



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    FARID AKHUNDOV
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