Routing

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Default routes

  • 1.  Default routes

    Posted 30 days ago

    Hello guys !

     

    Im trying to config 3 AS BGP with OSPF, but I have no idea how to config the Default routes in the ASBR Routers.

     

    i want to ping from VMX1  ( Lo0: 10.100.100.1) to the destination VMX6 ( lo0: 10.100.100.6). 

     

    I need your help please , thanks 

     

    Bildschirmfoto 2020-11-05 um 10.53.11.png



  • 2.  Re: Default routes

    Posted 30 days ago

    Hello,

    You don't need default routes in ASBRs.

    In fact, the whole internet operates without default routes, and it's called Default Free Zone (DFZ) for a reason.

    As for pinging between VMX loopbacks, You only need to announce specific /32 prefixes between AS, with nexthop-self export policy on ASBRs.

    HTH

    Thx

    Alex  



  • 3.  Re: Default routes

    Posted 30 days ago

    Hello Alex, 

     

    should it work without IBGP? because I just configered OSPF and EBGP. VMX1 has only OSPF

     

    maybe you can explain to me in which scenario should I have IBGP + OSPF. 

     

    thanks 



  • 4.  Re: Default routes

    Posted 30 days ago

    Hello,

    It will work without IBGP.

    But if You are interested in best practices, then, on a very high level :

    1/ Your IGP should ideally contain only loopbacks, less ideally loopbacks+link subnets

    2/ Your customer routes should be in IBGP

    3/ You should advertise Your summarized customer routes and Your own summarized infra routes (DNS subnets, company portal, etc) over EBGP to the outside world. 

    Anything else is good for lab practicing/exam prep only.

    HTH

    Thx

    Alex 



  • 5.  Re: Default routes

    Posted 30 days ago

    Hello!

     

    I tried many times but its still docent work!! can you please write the correct configuration for ASBRs, it will help me und will be helpful for others. 

     

    thanks 



  • 6.  Re: Default routes

    Posted 29 days ago

    Hello,

    Here is the simple example R-6 config for You.

    Assuming VMX6 lo0.0 IP address is 203.0.113.6 and R-6 lo0.0 IP address is 198.51.100.66, then

     

    set routing-options autonomous-system 64544
    
    set protocols bgp group EBGP peer-as 64533
    set protocols bgp group EBGP neighbor 10.100.46.1
    set protocols bgp group EBGP export PL-VMX6-LPBK
    
    set protocols bgp group IBGP type internal
    set protocols bgp group IBGP local-address 198.51.100.60
    set protocols bgp group IBGP neighbor 203.0.113.6 ## VMX6 lo0.0 IP address
    set protocols bgp group IBGP export PL-NHS
    
    set policy-options policy-statement PL-NHS then next-hop self
    set policy-options policy-statement PL-NHS then accept
    
    set policy-options policy-statement PL-VMX6-LPBK term 1 from route-filter 203.0.113.6/32 exact
    set policy-options policy-statement PL-VMX6-LPBK term 1 then accept

     

     

    HTH

    Thx

    Alex



  • 7.  Re: Default routes

    Posted 29 days ago

    Hello,

     

    thanks for your response. Hin: R-6 and VMX6 are one Router ( RE+ FPE ) but anyway I will apply your configuration on VMX2 in AS 64522.

    i have one more question please, what if there too many Routers in AS must I config a routing policy on ASBR ( from route-filter xx.xx.xx.xx/32 exact ) for each Router? 

    thanks 


    #h


  • 8.  Re: Default routes

    Posted 29 days ago

    Hello,

    You must configure BGP export policy saying "from route-filter X.Y.Z.W/NN" everywhere where You want to inject a route into BGP.

    So, if  "X.Y.Z.W/NN" isn't in BGP - check with "show route protocol bgp  X.Y.Z.W/NN"  it should be empty if route is not in BGP - then please configure BGP export policy.

    HTH

    Thx

    Alex