cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
849
Views
0
Helpful
2
Replies

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

rafat0426
Level 1
Level 1

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

milan.kulik
Level 10
Level 10

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

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

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: