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Beginner

when a router receive update from igp and BGP, than it shoud use onle BGP in routing table

Hi,

in my scenario the branches are connected with multiple isps

lets say X is advertising its route to both ISP's from 3 exit points ,

1. when this route is reaching at Router C through ISP-B , i am blocking it to advertising it to ISP-A form this router

2. when this route is going to Router E from Router X it is redistributing in BGP cloud through ISP-A means this Route is Receiving By Router C Via ISP-A , Router D via ISP-A and Router A via Router C which is learnt from  ISP-A

i).     at Router  A i block to redistributre into ISP-B

ii).    at Router D while redistributing into IGP i set the metric high , because when it sends this route to X it should not use this route.

3.  when this route is reaching Router D from Router X it is redistributing in BGP Cloud through ISP-A , means this route is aging reaching to Router C via ISP-A , Router E via ISP-A and Router A via Router C which is learnt from  ISP-A.

    i).     at Router  A i block to redistributre into ISP-B

    ii).    at Router E as this coming as BGP and as to keep BGP route in the routing table i decrease the weight to '0' & local-preference to '90' for this route, than i am receiving this route in the routing table of Router E as BGP

till here everything is oK.

Problem: when Link (Primary ) B/W Router D and ISP-A goes Down

1. Route X is advertising 192.168.110.0 through Router E redistributing IGP (OSPF) into BGP , but branches are getting this route in the routing table packet is getting dropeed  ( unless i change local preference for this path to 100 in Router E configuraiotn where i have set '90' previously   ) in the BGP Cloud only.

2. i noticed that Router C is not keeping BGP route in the routing table ( unless i change local preference for this path to 100 in Router E configuraiotn where i have set '90' previously   ) even i set local-preference fo this route to '50' in the Router C configuration it is not keeping BGP route in the routing table.

  it is using which it is learning from Router A via ISP-B

so i want this route as BGP in the routing table of Router C , when the link B/W Router D and ISP-A link goes DOWN ( without changing local-preference in Router E which i set 90 i want use as 90 only  )

Note: if i increase local preference in Router E to 100 every thing is working fine no issues ( but you know if i increase this to 100 when link B/W Router D and ISP-A come up, in the Router E for 192.168.110.0 route it will use as IGP (OSPF) not the BGP )

can any one suggest me , how to do this or am i missing any thing  . kindly find attached diagram for your reference.

2 REPLIES 2
Advocate

Re: when a router receive update from igp and BGP, than it shou

Hi,

it's not  easy to understand your design.

Many questions coming to my mind:

Are all your routers D,E,X,F using the same BGP AS number? (Is X running BGP at all?)

Are you running iBGP between any of them?

How is the BGP/OSPF (mutual) redistribution done?

Why are you blocking BGP prefixes, wouldn't be worth using as-prepending, e.g.?

Do you want to route via ISP-A between E and X?

BR,

Milan

Beginner

Re: when a router receive update from igp and BGP, than it shou

Hi Milan ,

Thakns for your reply ,

there is no IBGP is running b/w any of them, in current situation i dont want use IBGP b/w them as i need to to lot of work (as of now i cannot sit )

1. D,E,X,F using sameBGP AS Number 64837 and at A,B,C is also using 64837 but in my BGP configuration i add neighbour (IP) allowas-in Command

    i am able to recieve the routes

   B/W D,E,F,X i am using OSPF in same area '0' , A,B,C is also using OSPF internally

2. OSPF/BGP Mutual redistribution

  i attach the configuration file, in the file you can see at Router E configuration  ,

  under BGP route-map if i set local preference 100 in Router E for 192.168.110.0 route it will use IGP in Routing table

if i set local preference 90 in Router E for 192.168.110.0 router it will use BGP route in routing table this i want

at Router C it use bgp route in its routing table for 192.168.110.0  and every thing is Ok ,

but when link b/w Router D and ISP-A fails , Router C will use IGP route which it is learning through its IGP from Router A unless i change local-preference to '100' in Router E configuration.

at this time i tried changing local preference to '50' ( in Router E keeping Local-preference is "90' under bgp configuration route-map) in Router C keeping a route-map for the same route while redistributing into BGP. but NO USE

Milan  prepending is used to manipulate as path attribute right  , but in my scenario when link B/W Router D and ISP-A goes Down , the Router C is not keeping update which i am advertising from Router E with local preference 90  unless i set local-pre '100'.

Milan kindly Suggest

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