Default route flapped in the core switches

[bhalla.himanshu]

Hi All,

I have two nexus 7706 running in my DC which is further subdivided in to two vdc's. And we are running BGP in my WAN layer and OSPF in my CORE layer.  My core layer learns default routing information  from the above two WAN VDC's through OSPF(which is injected by BGP) but when the BGP/ISP_1 link goes down and BGP/ISP_2 link stable I observed that both of my default routes flapped in the core switches which I learned thru OSPF.  Need your inputs - Is it a bug or some misconfiguration ?

Thanks!

HB

[paul driver]

Hello

Sounds like bgp is advertising the default into ospf  conditionally -meaning when the bgp peering flaps- it loses its conditional  route which in turn removes the advertise default into  your igp.

res

Paul

[bhalla.himanshu]

Hello Paul,

I have dual home ISP connections and  here I am concern about why the secondary default route flaps/disappear from my routing table when primary ISP link goes down.

SW-CORE-01# show ip route vrf all

IP Route Table for VRF "TRT-DIRTY"

'*' denotes best ucast next-hop

'**' denotes best mcast next-hop

'[x/y]' denotes [preference/metric]

'%<string>' in via output denotes VRF <string>

0.0.0.0/0, ubest/mbest: 2/0

*via 10.20.70.5, Po2.70, [110/1], 1d00h, ospf-10, type-2

*via 10.20.70.17, Po3.70, [110/1], 1d00h, ospf-10, type-2

Thanks!

Regards,

Himanshu Bhalla

Output from CORE layer-