Cannot ping node IP when configured in route-domain.

Just a quick update: after some line by line setup checking, I found the issue.

The route-domain and self-IP are configured on the F5 as a /23 (255.255.254.0) network, however the three servers we were having issues with were configured with only /24 masks.

The health monitoring ICMP packets were being sent from the F5 to the servers and actually arriving, but since the servers IP addresses were in the begining of the /23 network and the self-IP address on the F5 was at the very top end, the servers replys were being sent to it's configured default gateway as it saw the destination was not on the local subnet (due to the incvorrect mask).

The problem arose due the default gateway being a Checkpoint firewall that was dropping the ICMP echo-replies as it did not see the originating echo-requests as they went direct! If this had just been a basic router the traffic would have completed it's jurney back to the F5, albeit by a different path than the outbound echo-request.

We tested changing the network mask on the three effected servers and immediatley they showed as available nodes on the F5.

Thnaks for the replies.