HSRP on trunk connected 6509's failing when standy shutdown

[jcowtan]

Senario:

Server (on VLAN1) is connected to 6509(A) directly usign a trunk port.

6509(A) and 6509(B) interconnected via an etherchannel trunk (Unique vlan network)

The User is on VLAN 34 connected to a 3750. The 3750 is uplinked to both 6509A&B using trunks that allow VLAN 1 and Vlan 34.

HSRP is user for VLAN 1 and 34.

6509A is root and active router for VLAN1.

6509B is root and active router for VLAN34.

Test: layer 2

When interface from 3750 to 6509B (active and root for VLAN34) is removed, 6509A takes over as expected.

Recovery when reconnected, works.

When the 3750 to 6509A interface is dropped, we loss all connectivity.

Test: Layer 3 (routing)

(We are using EIGRP)

When active router for VLAN 34 on 6509B is shutdown, 6509A takes over and no connectivity problems are seen (as expected).

When standby router (6509A) is shutdown - connectivity is lost. When reviewing HSRP on 6509A, it sees itself are the ACTIVE Router, but we has no connectivity. We have not touched VLAN1.

My thought was it might be the unique network between the 6509s...so I changed it to a trunk allowing VLAN1 and VLAN34.

Layer 2 test worked when either interface from the 3750 was pulled.

Layer 3 test failed when the standby router (6509A) was shutdown.

I am puzzled. The core design was to allow aternate path but it seems this is not working.

Is there a problem or is my design in error?

[gmarogi]

You can probably check the CAM table on the switches and the ARP table on the devices to check the mapping for the active router at any point of time. If this information is mapped correctly, I think you should not have any problem. The configuration is also needed to provide more help.

[nihal.akbulut]

Hi,

for the first problem; the link between 6509s must be trunk, because they have to communicate for HSRP per vlan. or there is a second way they can use for this communication: through the 3750 (if it has trunk links to both 6509). but the first way is preferable.

but what is the problem on your layer3 test? you say that you have no connectivity, do you mean that user-server connectivity? can you explain more about it?

[jcengh]

I agree with the other submitters that I would have to see the configuration. But, I hope what I can give you here helps. Since your layer 2 tests pass, it does not appear to be a physical layer problem. To understand your question, when you state that the standby shutdown causes loss of connectivity, do you mean after the primary goes down and then comes back up at which point the standby connection fails? If so, it may be that you are missing a preempt statement which would allow the primary connection, when it comes back up, to assume the active role from the standby. Preempt is needed regardless of the fact that the standby member for vlan 34 would have a lower priority than the active member of your HSRP group for vlan 34. You might also want to make sure that the gateways of your host devices are pointed to the phantom IP instead of the IP of a specific router. Yopu may have this all set, but it is just another check. Good luck.

Jason

[jcowtan]

Thank you all for your replys. I have finally got the system for more testing. I think I may be on to something.

For quick review:

We do have a trunk between the two 6509s (CS1, CS2).

When CS1 is Active (A) router for VLAN 1 and Standby (S) router for VLAN 34 and

CS2 is S for VLAN 1 and A for VLAN 34, failover works when interfaces or system on CS2 is shutdown.

However (and after all interfaces are up and recovered), when Standby VLAN 34 on CS1 is shutdown, VLAN 34 looses all connectivity.

How, when we change the A and S on both 6509s so that VLAN 1 and VLAN 34 are reversed, all tests pass!!!

So it seems we have a problem with what CS1 is doing. In looking at differences I see the following:

A)

CS1 runs IOS S72033-psv-mz.122-14.SX1.bin, and

CS2 runs IOS S72033-pk9s-mz.122-14.SX1.bin.

- IS this difference an issue for my problem?

B)

I see looking at the routing configuration that

CS1 has a static route for VLAN 34 to a remote interface on VLAN1 -

CS2 has no static entry.

(I think the static was left over from another test.)

Am I correct that when VLAN 34 is shutdown on CS1, the router will use the static - rather than "learn" a new route the VLAN 34?