Routing

Hi ,

I have Two mx series router and connected to  two ISP link like this 

                           ospf /ibgp

ISP1------MX1-------------------MX2---------ISP2

Getting default route from EBGP on both router and redistributing this default route from ebgp to ospf on both router and in my rest of the LAN using IGP protocol OSPF . Now i want to set preference on OSPF  that default route from ISP1 should be prefer compare to ISP2 and If ISP1 default route  is not present that it should go through ISP1. I have tried definning External type1 to MX1 and E2 route on MX2 .but the result is not satisfactory. the route which is first redistributed will install in my OSPF database and its not changing till i stop the redistributing.

Configuration :-

For that what i did that i have made a import policy on MX1 :-

show policy-options policy-statement bgp-to-ospf   
term 1 {
    from {
        protocol bgp;
        neighbor 10.0.21.2;
        route-filter 0.0.0.0/0 exact;
    }
    then {
        external {
            type 1;
        }
        accept;
    }
}

show policy-options policy-statement ospf-import
term 1 {
    from {
        protocol ospf;
        external;
        route-filter 0.0.0.0/0 exact;
    }
    then reject;
}

show protocols ospf  
export bgp-to-ospf;
import ospf-import;
area 0.0.0.0 {
    interface ge-0/0/0.0;
    interface lo0.0 {
        passive;
    }
}

After applying this policy on MX1 ,now my route is getting prefernce from only MX1 router only .

Is this policy is correct or wrong ?  please advice

I'm not sure that I completely understand what you are doing, but if you want to have MX1 use ISP1 if it is up, and MX2 use ISP2 if it is up, but use the other ISP if the directly connected ISP is down, it might be easier to bring up an IBGP link between the two MX routers and exchange default routes, just de-preference them so they are only used as a backup.

If you still also need to export a default route into OSPF for the internal network, you can setup an import filter on the MX routers so they don't learn the default via OSPF via the other MX (which would override the BGP default route).

Thanks for your reply



This is my requirement to redistribute default route from bgp to ospf because i have eight router in my internal network in ospf and default route should be reach to all router to reach internet.



I have one more query that in cisco when redistribute default route from bgp to ospf than they configured "default-information originate". also in juniper i have read that we need to configured some policy for generate the default route that it will active if next-hop is reachable.exaple is below :-



root@A#

show policy-options policy-statement filter-contributors

term 1 {

from {

neighbor 10.1.1.1;

next-hop 10.1.1.1;

}

then accept;

}

term 2 {

then reject;

}



root@A#

show routing-options

generate {

route 0.0.0.0/0 {

policy filter-contributors;

discard;

}

}



root@A#

show policy-options policy-statement ospf-default

from {

route-filter 0.0.0.0/0 exact;

}

then accept;



Now above policy will export in ospf .



But what i did that  i don't configured the generate route for default route creation and i direclty redistributed the default route in ospf  which receiving from bgp and its working.



show policy-options policy-statement bgp-to-ospf
term 1 {
    from {
        protocol bgp;
        neighbor 10.0.21.2;
        route-filter 0.0.0.0/0 exact;
    }
    then {
        external {
            type 1;
        }
        accept;
    }
}



Now my query is that what is actual requirement of generate the default route to redistribut in ospf because i can directly redistribute in ospf which is receiving from bgp.

Hi,

from your first post what I understand you have 2 ISPs and both of them advertise default route (pref 170) and you distribute this route through OSPF (pref 150) so each MX prefer the OSPF update.

If so you can change the preference of OSPF external routes on both MX routers

#set protocols ospf external-preference 175

So it will change the preference of OSPF exxternal routes only to 175

----------------

If your problem in the LAN 8 routers not prefering MX1 default route and prefer MX2 default route or which one come first you could change the metric in OSPF export policy on MX2 so it will solve your problem

MX2# set policy-options policy-statement bgp-to-ospf term 1 then metric 40

Mohamed Elhariry

JNCIE-M/T # 1059, CCNP & CCIP

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If this post was helpful, please mark this post as an "Accepted Solution".Kudos are always appreciated!

From your question:

---

@Jagdish11 wrote:

Now my query is that what is actual requirement of generate the default route to redistribut in ospf because i can directly redistribute in ospf which is receiving from bgp.

---

My understanding is that to export a default route into OSPF, you need to have a valid default route in your routing table.  It doesn't matter where it comes from, static or a routing protocol, but you need to have a default route in order to send it to OSPF.

Hi,

Thanks for your reply..

It means in my case ,i am getting  default route from bgp . So i didn't need to configured generate route for create the default route on my router...Is it correct ..

Actually i am confused due to an attached document..i have tried this but the generate route work as a aggregate route with preference 130 for default and its blackhole the traffic.

Attachment(s)

OSPF default route in JUNOS1.pdf   91 KB 1 version

OSPF default route in JUNOS.pdf   88 KB 1 version

Hi

Yes that's exactly what I mean try to make the configuration simple as much as you can you already receive default route from your BGP peer and this route in your routing table as long as your BGP session is up so you can depend on that route and redistribute into your IGP 

Thanks for your reply..

Finally i am not configuring the generate route for default route creation and just redistributing the default route from bgp to ospf..