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Why is a higher AD static route preferred over an lower AD iBGP route?

Posted: Sat May 08, 2021 12:48 am
by clovehitch
router=CCR1000-7G-1C-1S+
version=6.48

Setup:

2 routers with a single eBGP session to separate ISPs
iBGP between the routers.

Each router has a static default route to the ISP with AD set to 254
Each router is receiving a default route via it's eBGP session.


ISP-1 ISP-2
(ASN-20) (ASN-30)
| |
| |
router-a <----> router-b
(ASN-10) (ASN-10)


router-a route table
0 ADb 0.0.0.0/0 ISP-1 GW 20
1 S 0.0.0.0/0 ISP-1 GW 254
2 Db 0.0.0.0/0 router-b IP 200

if I shutdown router-a ISP-1 port:
0 A S 0.0.0.0/0 ISP-1 GW 254
1 Db 0.0.0.0/0 router-b IP 200

Is the lower AD iBGP route not being selected because the BGP best path algorithm is not being run once the selected route drops? If that is the case, how can I make it so the default route is only active if both bgp default routes are not in the table?

The scope and target scopes are at their defaults.

Re: Why is a higher AD static route preferred over an lower AD iBGP route?

Posted: Tue May 11, 2021 6:57 pm
by clovehitch
Any thoughts on this? Why would a higher AD static route be the active route over a lower AD iBGP route? I know the scope settings can change this but those are set to the default values.

Re: Why is a higher AD static route preferred over an lower AD iBGP route?

Posted: Wed May 12, 2021 7:07 pm
by clovehitch
Any ideas from anyone?

Re: Why is a higher AD static route preferred over an lower AD iBGP route?

Posted: Wed May 12, 2021 7:15 pm
by rextended
--> I know the scope settings can change this