Currently we have 2 routers connected by a point to point line which are themselves connected to different providers. This is to establish failover if the primary location A provider fails we would still have availability in Location B of both of our subnets. We advertise both subnets in both locations. This has provided us neary equal load balancing across both providers. However, we would like to have the majority, if not all of our traffic (in & out) using the preferred provider in location A unless the preferred provider or location A failed in which case location B and the backup provider would take over. I have seen several articles and postings on how to do this, and believe that a combination of local preference and AS prepending will take care of this but BGP is not my strong suit so I am looking for verification that my proposal is correct. Below is a brief diagram as well as the current routing configs and the proposed ones. Do I have this correct or is more needed? As always thank you and if more info is needed, please let me know.
Location A Rtr (x.x.x.0) ---------------------EBGP-----------PreferredProvider (b.b.b.b) | OSPF (z.z.z.0) | Location B Rtr (y.y.y.0)---------------------EBGP-----------BackupProvider (a.a.a.a)
Existing Routing configs:
-------------------------------------------------------------------------------------- LOCATION A
router ospf 1 log-adjacency-changes network x.x.x.0 0.0.0.255 area 0 network z.z.z.0 0.0.0.3 area 0 ! router bgp myasnumber no synchronization bgp log-neighbor-changes bgp dampening network x.x.x.0 mask 255.255.255.0 redistribute ospf 1 neighbor b.b.b.b remote-as preferredprovider neighbor b.b.b.b distribute-list ADVERTISE out neighbor z.z.z.1 remote-as myasnumber neighbor z.z.z.1 next-hop-self no auto-summary
ip access-list extended ADVERTISE permit ip x.x.x.0 0.0.0.255 any permit ip y.y.y.0 0.0.0.255 any
-------------------------------------------------------------------------------------- LOCATION B router ospf 1 log-adjacency-changes network y.y.y.0 0.0.0.255 area 0 network z.z.z.0 0.0.0.3 area 0
router bgp myasnumber bgp log-neighbor-changes neighbor a.a.a.a remote-as backupprovider neighbor a.a.a.a ebgp-multihop 2 neighbor a.a.a.a update-source Loopback0 neighbor z.z.z.2 remote-as myasnumber address-family ipv4 redistribute ospf 1 metric 1 neighbor a.a.a.a activate neighbor a.a.a.a send-community neighbor a.a.a.a soft-reconfiguration inbound neighbor a.a.a.a distribute-list advertised_network out neighbor z.z.z.2 activate neighbor z.z.z.2 next-hop-self no auto-summary no synchronization bgp dampening network y.y.y.0 mask 255.255.255.0 exit-address-family
ip access-list extended advertised_network permit ip y.y.y.0 0.0.0.255 any permit ip x.x.x.0 0.0.0.255 any
--------------------------------------------------------------------------------------
Proposed Changes indicated by ***
-------------------------------------------------------------------------------------- LOCATION A
router ospf 1 log-adjacency-changes network x.x.x.0 0.0.0.255 area 0 network z.z.z.0 0.0.0.3 area 0 ! router bgp myasnumber no synchronization bgp log-neighbor-changes bgp dampening network x.x.x.0 mask 255.255.255.0 redistribute ospf 1 neighbor b.b.b.b remote-as preferredprovider neighbor b.b.b.b distribute-list ADVERTISE out neighbor z.z.z.1 remote-as myasnumber neighbor z.z.z.1 next-hop-self no auto-summary
*** bgp default local-preference 200ip access-list extended ADVERTISE permit ip x.x.x.0 0.0.0.255 any permit ip y.y.y.0 0.0.0.255 any\\
-------------------------------------------------------------------------------------- LOCATION B
router ospf 1 log-adjacency-changes network y.y.y.0 0.0.0.255 area 0 network z.z.z.0 0.0.0.3 area 0
router bgp myasnumber bgp log-neighbor-changes neighbor a.a.a.a remote-as backupprovider neighbor a.a.a.a ebgp-multihop 2 neighbor a.a.a.a update-source Loopback0 neighbor z.z.z.2 remote-as myasnumber address-family ipv4 redistribute ospf 1 metric 1 neighbor a.a.a.a activate neighbor a.a.a.a send-community neighbor a.a.a.a soft-reconfiguration inbound neighbor a.a.a.a distribute-list advertised_network out
*** neighbor a.a.a.a route-map Traffic-out out neighbor z.z.z.2 activate neighbor z.z.z.2 next-hop-self no auto-summary no synchronization bgp dampening network y.y.y.0 mask 255.255.255.0 exit-address-familyip access-list extended advertised_network permit ip y.y.y.0 0.0.0.255 any permit ip x.x.x.0 0.0.0.255 any
*** route-map Traffic-out permit 10 *** set as-path prepend myasnumber myasnumber