Redistributing BGP to OSPF --- What will be the route ospf route type ?

[umeshpathrwal10]

Hi  

i  have  got  a below   topology . Wanted  to understand    route type  behavior  of  ospf .  HOW  route  from CE1  to  CE 2  and vicewill  be seen , will it be O , IA , E1 or E2  ospf  route. 

CE1 ----PE1--------MBGP------PE2 --------CE2 

Between CE1--PE1-- ospf in area 0 

Between CE2--PE2- ospf in area 0 .

At PE 1 & PE 2 ---  below  configuration exist 

router bgp 9730
vrf X
rd 9730:20522
address-family ipv4 unicast
redistribute connected
redistribute static
redistribute ospf 100 match internal external
!
!
!

router ospf 100
vrf X
timers lsa min-arrival 30000
redistribute bgp 9730
area 0
interface Bundle-Ether3.8365
network point-to-point
mtu-ignore enable
!
!
!
!

[Seb Rupik]

Hi there,

On the PE routers, when redistributing from BGP to OSPF the routes will appear as type E2. This is the default behaviour for routes learnt via redistribution.

cheers,

Seb.

[@confignetworks]

They will be seen in OSPF as E2 routes, this is the default behavior. 

As far as you don't specify in redistribution that you want routes to be redistributed in E1 routes, it wil be E2 routes.  

[umeshpathrwal10]

Hi 

Correct , E2   routes  will be the route  type after bgp to ospf  redistribution or any  IGP to ospf . 

But , here in mbgp  scenario , am observing IA ( Summary Net Link States (Area 0)) routes . can any one explain the reason  please . 

Ce1 ---  (o 10.221.27.0/24 )PE1--mbgp---Pe2---Ce2 (IA 10.221.27.0/24 )

[Giuseppe Larosa · Accepted solution]

Hello,

for OSPF to MP BGP some additional extended communities have been introduced for the so called OSPF emulation and MPLS area 0.0.0.0 superbackbone

in short if PE1 and PE2 use the SAME OSPfv2 id  (this is carried inside extcommunity OSPF domain id):

O, O IA route will become O IA routes and the the reconstucted LSAs will be of type 3

O E1, O E2 will be external as expected

if PE1 OSPFv2 process-is <> PE2 OSPF process-id or a domain is set on purpose in that ALL remote routes will be O E2 I have used this design in a customer for NG MVPN transporting video streams over MPLS.

Also the Down bit is set providing a mechanism to support multihomed VRFs.

Have a read of RFC

https://tools.ietf.org/html/rfc4577

Hope to help

Giuseppe Larosa

[rais]

This is because you have MPLS in the core. CE1 and CE2 mimic as if you are directly connected. HTH.