OSPF ring and HSRP

[tallpaulroe]

Hi guys

i have an OSPF ring of around 10 c3560's

the exit from the ring to the WAN is via 2 c3560's using HSRP.

my concern is that if i understand HSRP correctly one router acts as main and the other as standby. If the main fails then the standby takes over and the OSPF will sort the rest of the routers.

However how to protect against a failure of a router halfway around the ring?

any info would be appriciated

cheers

[lgijssel]

Should not be a problem.

OSPF will take care of this.

regards,

Leo

[tallpaulroe]

what makes think it wont wokr is that under normal condition any data

for the networks on the ring are forwarded to the Virtual IP Address of the 2 HSRP routers.

If one of these fails then HSRP switches to the other the OSPF in the ring takes care of the rest.

But if a router halfway around the ring fails, one side of the ring would work ok, and OSPF could be made to get the other half of the ring to work ok by using 2 default routes with different costs.

The problem that i think may happen is that any data sent to the ring will be sent to the Virtual IP address of the pair of HSRP routers and only one is active and the OSPF should have told it that half the ring has gone so where does this router now forward the data for that half of the ring that appears to have gone?

[lgijssel]

What makes you think this ring only supports sending traffic in one direction?

Normally, when it breaks somewhere halfway, the traffic is simply sent in the other direction as this becomes the shortest path (if it is not already).

regards,

Leo

[Florin Barhala]

This is more like a fairy tale; post your configs if necessary then tell us how can we help you.

One idea I have would be to use EEM on each router os if ring break up, then by EEM you trigger some changes.

[shehzadtesleem]

share topology please; it should keep on working if ring is broken OSPF will care that and HSRP will continue to run as it was before.

[tallpaulroe]

as anticipated this did not work

i did a test with 7 routers R0->R7

R1->R6 form a ring with R1 at the start and R6 at the end, R1 and R6 are both connected to R0 and R1 and R6 run HSRP

all works fine unless you break the ring in the middle and then HSRP does not switch over and OSPF send any data back to R0 wh0 then sends it back to R1 who sends it back to R0 and it just carries on like that

The solution was to put a link from R1 to R6 thus having a complete ring, then all works fine

cheers