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IP SLA stopped working after upgrade to 3750X with 15.0(2)


We have a series of 3750G access switches running 12.2(52)SE with IP SLA responder enabled. They are polled by a router outside a firewall. All switches reside on a Management VLAN using RFC1918 IPs with their default gateway address in the same Management VLAN. In order to allow router access to the IP SLA responder we provided the ability to route the packet back to the monitor by configuring an SVI. The SVI IP corresponds to the configured Host VLAN on these switches. This worked and still works great on the 3750G switches. When we upgraded some switches to 3750X platforms with IOS 15.0(2) the IP SLA monitor for the responders on the 3750X switches started timing out.

As before, we see the router sending the IP SLA control packet to the SVI's IP address -- the response contains the switch's RFC1918 address rather than the SVI IP-address and therefore can't get back to the router.

IP SLA functionality works fine on the 3750Xs as long as the  queries stay on the Management VLAN. So, it's apparent that the issue seems to be with routing when sending the control packet to the SVI IP.

Any ideas if there were changes in 15.0(2) that would induce this behavior? Do we have other options than to create a single-host static route for the router on the 3750Xs? Any help would be much appreciated.


= Uwe =

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