Routing to secondary default route not working when primary route is unavailable

[WingFan19]

I have a router at a branch location that is connected to our main office via T1 on S0/1/0.  Under normal operations, all traffic (LAN & Internet) is routed to our main office thru S0.  We have installed a backup Internet circuit for DR purposes that is conected to FE0/1.  I have set a secondary default route with a higer metric to route out thru FE0/1, but it is not routing when S0/1/0 becomes unavailable.  It will route if I delete the default route that goes to S0/1/0, but it doesn't automatically fail over to the higher metric route when S0/1/0 "fails".  Here is pertinent config info:

interface Null0
no ip unreachables
!
interface FastEthernet0/0
description Sandy Local Lan
ip address 10.1.3.254 255.255.255.0
no ip redirects
no ip unreachables
ip route-cache flow
duplex auto
speed auto
no mop enabled
!
interface FastEthernet0/1
ip address 192.168.100.5 255.255.255.0
no ip redirects
no ip unreachables
ip route-cache flow
duplex auto
  speed auto
no mop enabled
!
interface Serial0/1/0
description To Glisan
ip address 10.1.254.6 255.255.255.252
no ip redirects
no ip unreachables
ip route-cache flow
no ip mroute-cache
no fair-queue
!
interface Serial0/2/0
no ip address
no ip redirects
no ip unreachables
shutdown
no fair-queue
!
router eigrp 1
network 10.0.0.0
network 192.168.100.0
auto-summary
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 10.1.254.5
ip route 0.0.0.0 0.0.0.0 192.168.100.1 20
!

What am I missing?  Like I said it will route to thru 192.168.100.1 if I manually remove the route to 10.1.254.5 (partner IP to S0/1/0).  But if I "fail" the circuit by either shutting down DSU connected to S0/1/0 or setting S0/1/0 to shutdown, it still tries to route to 10.1.254.5.

Any help is greatly appreciated.

Eric

[Jerry Ye]

Try this

ip route 0.0.0.0 0.0.0.0 serial0/1/0 10.1.254.5

HTH,

jerry

[lgijssel · Accepted solution]

Hi,

EIGRP has an entry for network 10.0.0.0 and because auto-summary is on, it thinks it still has a route to 10.1.254.5 through fa0/0.

Configure "no auto-summary" under router eigrp 1 and it should work as long as int s0/1/0 goes down.

regards,

Leo

[cadet alain]

Hi,

post output of sh ip route 0.0.0.0  before and after shutting the primary

Regards.

Alain.

[WingFan19]

no auto-summary was the trick.

Thanks for the help.

[WingFan19]

@jeye & lgijssel

I'll try these suggestions and post results here.  Probably not for a week.

@cadet alain

Here's the IP route when S0/1/0 is up.

Gateway of last resort is 10.1.254.5 to network 0.0.0.0

     10.0.0.0/8 is variably subnetted, 7 subnets, 3 masks
D       10.1.10.0/24 [90/2172416] via 10.1.254.5, 6d01h, Serial0/1/0
C       10.1.3.0/24 is directly connected, FastEthernet0/0
D       10.1.1.0/24 [90/2172416] via 10.1.254.5, 6d01h, Serial0/1/0
D       10.0.0.0/8 is a summary, 6d01h, Null0
D       10.1.50.0/24 [90/2172416] via 10.1.254.5, 6d01h, Serial0/1/0
C       10.1.254.4/30 is directly connected, Serial0/1/0
D       10.1.254.0/30 [90/2681856] via 10.1.254.5, 6d01h, Serial0/1/0
C    192.168.100.0/24 is directly connected, FastEthernet0/1
S*   0.0.0.0/0 [1/0] via 10.1.254.5

Unfortunately I can't take it down in the middle of business to get the route table when it's down.  As I recall, dynamic routes drop off (except 10.0.0.0/8), but the Gateway remains at 10.1.254.5.

[manish arora]

Hi Eric,

The configured Static route will not disappear if the link fails or you manually shut down the interface. The static route is like a Road Sign which will stay their even if the Road that it is pointing too was swept away in the Flood .. ;-) .

For what you are looking for is "IP SLA configuration" that will track the Primary Link and will switch to the Back link in case the primary fails for default STATIC routing . Here's how it is done :-

http://www.cisco.com/en/US/docs/ios/12_3/12_3x/12_3xe/feature/guide/dbackupx.html

Thanks

Manish

[cadet alain]

Hi Manish,

if the interface is down then the floating static route will get inserted.

reliable static routing is only needed when the line protocol won't get down even though there is no more reachability to the other side which is down like in Frame-relay physical interface or ethernet switched environment.

If what i'm saying is totally wrong please tell me so I can correct my mistakes.

I think Leo has pointed the problem with the EIGRP summary route used in the recursive lookup.

Regards.

Alain.

[lgijssel]

cadet alain wrote:
I think Leo has pointed the problem with the EIGRP summary route used in the recursive lookup.

Thanks mate!

Appreciation from a knowledgeable collegue is as good as getting rated.

(which is probably not going to happen for this one anyway.)

Leo

[Jerry Ye]

This problem can be solve with both solutions:

1: change the static route to include an outgoing interface

ip route 0.0.0.0 0.0.0.0 serial0/1/0 10.1.254.5

2. do no auto-summary under EIGRP process

Both will work since the static route know where to find the next-hop other than using the summary route to find 10.1.254.5.

Regards,

jerry

[manish arora]

Hi Alain,

I think you are correct on this , I missed that horribly. I just labbed it up and it appears that the floating route comes up when you shutdown the serial interface.  Thanks for catching that .

Thanks

Manish