We have a S4 as a border router. Can not ping it or ssh. I can console into it. I can only ping our ISP gateway and nothing else (internal or external). This router is part of BGP. Traffic is going through, just can't seem to be able to log into it or ping it.
At this point I'd suggest logging a case with the GTAC so we can help you trace down why this is happening. Assuming the traffic is not getting blocked by ACLs, Policy or firewalls then Ping should at least be working
Are there any ACL's applied to the interfaces or policy applied to the ports on this S4? Or possibly a service ACL? Also are you trying to ping/telnet interfaces that are in a VRF?