Enable probe caching for WAN visibility. By default, probe caching is disabled in RiOS 5.5 and later.

None

With probe caching, the client-side SteelHead caches the autodiscovery probe response from the server-side SteelHead when trying to reach a specific server. On subsequent attempts to reach the same server, the SteelHead uses the already cached probe response. On those attempts, the client-side SteelHead sets up a session directly to the peer SteelHead within the 7800 inner channel, bypassing the autodiscovery process since it was successful with the previous attempt. By default, probes are cached for 10 seconds.

With probe caching enabled, SteelHeads still perform autodiscovery. Probe caching simply saves some steps during auto-discovery if you are going to the same destination host. With probe caching disabled, every new TCP session performs autodiscovery, instead of just some of the new TCP sessions.

Use the show in-path probe-caching command to determine if probe caching is enabled on the SteelHead.

When the server-side SteelHead is on a VLAN trunk and simplified routing is enabled, Riverbed recommends disabling probe caching on all the remote SteelHeads. This is because the connection request inside the 7800 inner channel might not have the correct VLAN ID. Because the request arrived on the inner channel, the VLAN ID in the request would be same as the SteelHead in-path VLAN. If the server is on a different VLAN than the SteelHead, the request will not have the correct VLAN ID and there is no easy way to determine it. With probe caching disabled, the SteelHead will always get the SYN with original client and server IP addresses and the router adds the correct VLAN. You only need to disable probe caching on client-side SteelHeads.

If you have multiple SteelHeads connected with WCCP, you might see many forwarded connections and a larger than expected amount of data sent in the Neighbor Statistics report. (You configure neighbors when you enable connection forwarding.)

The probe caching mechanism allows some sessions to get established on the wrong SteelHead. Disabling this mechanism ensures the routers have a chance to redirect every SYN packet to the correct SteelHead, preventing connection forwarding from occurring.

To avoid incorrect forwarded connections, disable probe caching on the client-side SteelHead which instructs the client-side SteelHead to not cache the probe response.

For details, see the SteelHead Deployment Guide.

The no command option disables probe caching.

SteelHead CX, SteelHead EX, SteelHead-v, SteelHead-c

show in-path probe-caching, in-path rule auto-discover, show in-path peering oobtransparency