Contract work on an OT infrastructure separation. Two OT sites are being carved out of their parent company in an M&A transaction, and the OT control environment has to run on the acquirer's own services from cutover. You work in a small team under the lead firm on the program.
The role
Own the network workstream end to end: design it and build it. Find out what is on the network at both sites, decide what has to cross the IT/OT boundary at cutover, build the changes, and run the network cutover on site. The work centers on L3.5 (the IT/OT DMZ) and the in-scope L3 network.
What you will do
· Lead a three-week remote assessment of both sites and turn the seller's incomplete drawings into a current-state network picture
· Map the connectivity at each site: every flow that crosses the IT/OT boundary, with ports, protocols, zones and conduits, as the basis for the acquirer's firewall cutover
· Design the L3.5 DMZ and the L3 network changes needed at cutover, and keep the network rows of the disposition register: what transfers, what is bridged, what is replaced
· Stage the network devices and any virtual stand-ins, and take over the existing site switches with credentials, config backups, and AAA, syslog and SNMP re-pointed to the acquirer
· Stand up DHCP relay, device AAA and the time source at L3
· Agree the monitoring sensor points with the OT Cybersecurity Engineer
· Write the network section of the cutover runbook, run isolation tests and test plans, execute the network cutover steps on site, and make the network rollback recommendation
· Support hypercare, keep diagrams, IP plans and configs current in the team repository, and report network progress, risks and open questions to the lead firm
What you bring
· 10+ years in enterprise network engineering, with lead or design responsibility and recent hands-on configuration work
· IT/OT segmentation using the Purdue model and ISA/IEC 62443 zones and conduits
· DMZ design under a restrictive protocol policy, using relays, proxies and per-flow rules
· Cisco routing and switching at CCNP level or equivalent, including VLANs, OSPF and BGP
· TACACS+ or RADIUS, DHCP relay and NTP
· Led and executed at least one live cutover to a fixed date with a written rollback plan
· Comfortable presenting a design to a client security team and working from a runbook in a change window
Nice to have
· Divestiture, carve-out or merger separation experience
· Check Point and Palo Alto firewall policy
· OT network monitoring sensor placement (Nozomi, Dragos or Forescout)
· Cisco Catalyst 9800 wireless controllers and access-point re-adoption
· Catalyst 8000V or 9800-CL virtual appliances
· Scripting for config generation (Python, Ansible)
· CCIE, GICSP, PCNSE or CCSE