Auto-fail over not working

[Forbes Jenalyn Rose]

Hi guys,

We have two router on our network, each router is connected to two different ISP. When I perform an auto-fail oever test (If ISP A is down on router A, internet connection should not be affected because router B with ISP B is still connected and vice versa), the first router worked perfectly. However, on the second router, it takes 3-5 minutes to be able to go online again with ISP A. So there was downtime...

Could anyone please help me on this?

Here's the config:

Router A:

interface GigabitEthernet0/1

description upstream to ISP A

ip address 210.xxx.xxx.xxx 255.255.255.252

load-interval 30

duplex full

speed 100

media-type rj45

Router B:

interface GigabitEthernet0/1

description upstream to ISP B

ip address 125.xxx.xxx.xxx 255.255.255.252

duplex auto

speed auto

media-type rj45

Could this load-interval be the reason?

I would appreciate your soonest response.

Regards,

Jenalyn Forbes

[blau grana]

Hello,

Could you please describe your connection little bit further, connection between routers, routing protocols, configuration...

load-interval is definitely not the cause of your problems ->

https://supportforums.cisco.com/thread/149119

Best Regards

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[Forbes Jenalyn Rose]

Hi Blau,

Thank you for your response.

Attached is our partial network diagram and router config.

Routes to internet is through BGP and routes to internal is through OSPF.

Regards,

Jenalyn

[Abzal]

Hi,

Issue might be because you have wong iBGP peering between routerA/routerB.

RouterA:

interface Loopback0

ip address 116.1.7.1 255.255.255.255

router bgp 45941

no bgp fast-external-fallover

bgp log-neighbor-changes

neighbor iBGP peer-group

neighbor iBGP update-source Loopback0

neighbor iBGP version 4

neighbor eBGP peer-group

neighbor eBGP version 4

neighbor 116.1.6.1 remote-as 12345

neighbor 116.1.6.1 peer-group iBGP

neighbor 210.1.2.3 remote-as 6789

neighbor 210.1.2.3 peer-group eBGP

RouterB:

interface Loopback0

ip address 116.1.6.1 255.255.255.255

router bgp 45941

no bgp fast-external-fallover

bgp log-neighbor-changes

neighbor iBGP peer-group

neighbor iBGP update-source Loopback0

neighbor iBGP version 4

neighbor eBGP peer-group

neighbor 116.1.7.1 remote-as 45941

neighbor 116.1.7.1 peer-group iBGP

neighbor 125.1.2.3 remote-as 6648

neighbor 125.1.2.3 peer-group eBGP

Does second router have a default route?

Hope it will help.

Best regards,
Abzal

[Forbes Jenalyn Rose]

Hi Abzal,

Sorry, it's a typo error when I edit the config for you.

It is actually:

Router A:

router bgp 12345

no bgp fast-external-fallover

bgp log-neighbor-changes

neighbor iBGP peer-group

neighbor iBGP update-source Loopback0

neighbor iBGP version 4

neighbor eBGP peer-group

neighbor eBGP version 4

neighbor 116.1.6.1 remote-as 12345

neighbor 116.1.6.1 peer-group iBGP

neighbor 210.1.2.3 remote-as 6789

neighbor 210.1.2.3 peer-group eBGP

Router B:

router bgp 12345

no bgp fast-external-fallover

bgp log-neighbor-changes

neighbor iBGP peer-group

neighbor iBGP update-source Loopback0

neighbor iBGP version 4

neighbor eBGP peer-group

neighbor 116.1.7.1 remote-as 12345

neighbor 116.1.7.1 peer-group iBGP

neighbor 125.1.2.3 remote-as 6648

neighbor 125.1.2.3 peer-group eBGP

Sorry for the confusion.

Please check where else can be the possible cause of this issue.

Regards,

Jenalyn

[Abzal]

Hi Jenalyn,

Ok, I see.

Then question: do you have default routes from perspective ISPs on both routers? If yes, then I suppose router/switch that connected to both routers(routerA/routerB) might be doing load-balancing between them. You may check it.

And try to change OSPF configuration on routerA/routerB:

router ospf 1

no default-information originate always

default-information originate

Because with always keyword router will be advertising default route to other OSPF routers even it doesn't have one.

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801ec9f0.shtml

Hope it will help.

Best regards,
Abzal

[blau grana]

Also for iBGP neighbors you should have configured next-hop-self ->

router bgp 12345

neighbor iBGP peer-group next-hop-self

Beause iBGP peers do not change next hop IPs when advertising prefixes to iBGP peers by default. This could be problem, RouterA will not use prefixes via RouterB and vice versa because next hop is unreachable for them.

You should either configure next-hop-self for iBGP peer-group or use OSPF to advertise next-hops -> include WAN interfaces in OSPF but make them passive.

Best Regards

Please rate all helpful posts and close solved questions