4.9 redistribution???

Hi everyone,

does anyone know why r1 & r2 have this configed: distance ospf external 171 and r5 under router rip : distance 109 configed.



  • excellent answer in lab 2 ver4 section
  • R1 and R2 have problem when redistribution. OSPF external routes will prevail and EIGRP external Routes will be owned by OSPF in the Eyes of R1 and R2 so R5 will think OSPF owns it all and R1 and R2 will start pointing at each other being source of Routes that are actually in EIGRP. thats why we made OSPF external as 171 so R1 and R2 don't asume OSPF being owner of EIGRP external Routes. however doing that we made another problem coz now OSPF external Routes will be owned by EIGRP. since the only OSPF external Routes that are valid here are coming from R5 RIP Routes, it will be ok this way

    - R5 redistributes routes from RIP into OSPF
    - R5 is configured to have administtrative distance of 109
    now coz of that change Redistrubted RIP routes will always be sourced from the RIP network in R5 and whatever OSPF router claims otherwise R5 will not listen to him coz when comparing the administrative distances RIP wins.
    - R1 recieves the RIP routes from R5 as ospf external.
    - R1 redistribute those routes into EIGRP not coz of administrative distance but coz they are new routes that don't even exist in the EIGRP network. ( WE ONLY USE ADMINISTRATIVE DISTANCES WHEN WE COMPARE BETWEEN 1 SAME ROUTE BEING OWNED FROM 2 PROTOCOLS)
    - R3 recieve the Routes as External EIGRP from R1
    - R2 recieve those routes from R3.
    - R2 starts comparing between RIP routes in EIGRP network and OSPF network regarding administrative distances.
    - R2 judge for EIGRP

    now a ping to RIP routes from R2 will make the route go from R2 >>> R3 >>> R1 >>> R5 and BACK smoothly

    - R2 will not poison R1 with RIP routes from OSPF side coz there is already a source for those which is R5 he cant claim he is sourcing when someone else is sourcing in the same Protocol.
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