Network Infrastructure

Office is offline. Diagnose: ISP vs onsite hardware vs config — and prove it before paying for an emergency engineer who finds 'no fault'.

A loop has been introduced — broadcast traffic is saturating the LAN. Find and break the loop, then add prevention.

In VLAN-separated or micro-segmented environments, DNS resolution fails when client-facing resolvers lack conditional forwarders pointing to authoritative servers in remote segments, or when firewall…

Wi-Fi network segmentation and client isolation misconfigurations allow wireless clients to communicate with each other or reach network segments they should be blocked from, undermining guest/corpor…

VLAN misconfiguration, missing or incorrect inter-VLAN routing (SVI/sub-interface), and firewall or ACL rule errors cause complete or partial loss of communication between network segments, unexpecte…

All users on one or more LAN segments lose internet and inter-site connectivity when the router or Layer 3 switch providing the default gateway crashes, reboots, or loses its routing table. HSRP/VRRP…

Recent firewall or network change has caused an outage. Roll back fast, then diagnose what was wrong about the change.

A recent firewall rule insertion, reorder, or firmware upgrade causes previously working internal-to-DMZ, inter-VLAN, or site-to-site traffic to fail silently or with application errors. Root causes…

When a Cisco ASA performs NAT and maps internal hosts to outside addresses, upstream OSPF routers (e.g., Juniper MX5) have no routing information for that outside address space because the ASA does n…

A network loop occurs when multiple active Layer 2 paths exist between switches, causing broadcast storms that rapidly degrade or completely halt network connectivity for all users. Resolution requir…

CVE-2026-0300 is a CWE-787 buffer overflow in the PAN-OS User-ID Authentication Portal (Captive Portal) allowing unauthenticated remote code execution as root via specially crafted packets. Affected…

CVE-2026-0265 is a signature verification vulnerability in PAN-OS that allows unauthenticated remote attackers to bypass authentication when Cloud Authentication Service (CAS) is enabled on a login i…

The Windows Server DHCP service stops unexpectedly or fails to issue IP addresses following corruption of the Jet-engine-based lease database (dhcp.mdb). Corruption typically results from sudden stor…

The Windows Server DHCP service stops unexpectedly or ceases issuing IP addresses when the dhcp.mdb Jet engine lease database becomes corrupted. Corruption typically follows sudden storage outages, u…

CVE-2026-0257 is an authentication bypass in PAN-OS and Prisma Access affecting deployments where GlobalProtect portal or gateway authentication override cookies are enabled and Cloud Authentication…

An HTTP 504 Gateway Timeout is returned when a reverse proxy, API gateway, or load balancer (e.g., Nginx, HAProxy, AWS ALB, IIS ARR) fails to receive a timely response from the upstream application s…

Connection refused and connection timeout errors indicate TCP connection establishment failures to a target service. Connection refused means the target host is reachable but no process is listening…

HTTP 503 Service Unavailable is returned when the web server or reverse proxy cannot reach a healthy backend to fulfil a request. The failure originates at the web server process, application pool, o…

An HTTP 502 Bad Gateway error is returned when a reverse proxy, load balancer, or API gateway receives an invalid or no response from an upstream backend server. Root causes include the backend proce…

DHCP address assignment fails for clients connected via managed switches, wireless access points, or across VLAN boundaries, causing clients to fall back to APIPA (169.254.x.x) addresses. The root ca…

DHCP failures spanning switches, WAPs, and VLANs occur when clients cannot obtain IP addresses due to misconfigured DHCP relay agents (ip helper-address), VLAN trunking errors, or an unreachable/exha…