Switching and routing
Campus and data centre switching, routing, VLANs, spanning tree, first-hop redundancy and the change control around them.
Configurations are backed up on change and held in version control, with a diff available for every incident review.
A rollback that takes minutes and does not need the original engineer.
WAN and SD-WAN
Site-to-site connectivity, SD-WAN overlays, path selection, quality of service and failover behaviour that has been tested rather than assumed.
Failover is exercised on a schedule, because a standby path nobody has cut over to is a hypothesis.
Failover proven, with the switchover time recorded.
Wireless
Controller and access point management, RF planning, roaming behaviour, guest and corporate separation, and density for spaces that fill up.
Surveys are repeated after floorplan changes, which is when most wireless complaints actually start.
Coverage that survives a full room.
Remote access and VPN
Site-to-site and client VPN, certificate lifecycle, MFA integration and the capacity to absorb a day when everyone works from home.
Certificate expiry is inventoried and alerted, because that is the outage everyone has had at least once.
Remote access that holds on the day it is needed most.
Carrier and vendor management
Circuit inventory, contract and renewal dates, fault raising, escalation through the provider's tiers, and credit claims where the SLA was missed.
We arrive at the carrier with logs and timings, which shortens the argument considerably.
One party chasing the provider, and it is not your team.
Network security controls
Firewall rule lifecycle, segmentation, access control lists and the review process that stops rule bases growing forever.
Rules are reviewed on a cycle with owners named, so temporary exceptions do not become permanent by default.
A rule base you can explain to an auditor.