This document provides a repeatable validation methodology to prove the Guest network controls are effective.
Rule: configuration without validation is assumption.
1) Validation model (what we are proving)
We validate four core claims:
Guest-to-Guest isolation works (reduce lateral abuse)
Boundary controls hold (Guest cannot pivot where it shouldn’t)
DNS is not leaking internal knowledge (no internal recon surface)
Guest remains usable under abuse (basic DoS resilience)
This aligns with Zero Trust thinking: do not trust network location; validate control effectiveness.
2) Test prerequisites
Two or more guest endpoints (laptop + phone, or two laptops)
One endpoint with packet capture tooling (e.g., Wireshark)
Ability to observe firewall logs/flows and DNS logs (ideal)
A clear list of intended allowlist destinations (DNS resolvers, portal VIP/FQDN)
3) Test suite A — Client isolation (Guest protection against Guest)
A1 — Peer reachability (L3)
Procedure
Connect Client A and Client B to Guest SSID
Attempt:
ICMP ping A↔B
TCP connect attempts to common ports (80/443/445/3389/22) from A to B
Pass condition
Peer traffic blocked (unless explicitly intended)
Why
Prevents direct scans and opportunistic lateral exploitation (MITRE: T1046).
A2 — Peer discovery via ARP/ND observation
Procedure
Run packet capture on Client A
Observe ARP (IPv4) or ND (IPv6) activity
Attempt to infer if peers are discoverable and reachable
Pass condition
You may see some broadcast/ARP; however, you should not be able to build stable peer sessions.
No successful peer connectivity.
Note If your platform explicitly does not isolate multicast (e.g., Cisco 9800 P2P blocking), document the residual exposure and treat it with separate controls.
A3 — Multicast / service discovery exposure
Procedure
Observe mDNS/SSDP traffic patterns
Determine whether clients can discover other services (printers, casting, etc.)
Pass condition
For strict Guest: discovery should be blocked or minimized.
If discovery is allowed for business reasons, document scope and apply rate limiting + monitoring.
4) Test suite B — Boundary enforcement (containment)
B1 — RFC1918 reachability tests
Procedure
Attempt traceroute/ping to representative RFC1918 ranges (10/8, 172.16/12, 192.168/16)
Attempt TCP connections to known internal IP ranges (should fail)
Pass condition
Guest cannot route to internal networks
Explicitly allowlisted exceptions are the only reachable internal-adjacent endpoints
B2 — Allowlist correctness (negative and positive testing)
Procedure
Confirm:
Portal VIP/FQDN reachable as intended
Guest DNS resolvers reachable
Confirm:
Non-allowlisted internal services are blocked
Pass condition
Only the allowlist works; everything else fails.
5) Test suite C — DNS security assurance (prevent recon, reduce blast radius)
C1 — Internal zone resolution attempts
Procedure
Attempt to resolve known internal-only domains (e.g., corp.local, internal subdomains)
Attempt to resolve common internal SRV records (if relevant to your environment)
Pass condition
Guest cannot resolve internal zones
Why DNS architecture is defined by RFC 1034/1035, and correct terminology matters for accurate validation.
C2 — Resolver enforcement (egress control)
Procedure
Attempt to query public resolvers directly (e.g., 1.1.1.1, 8.8.8.8) from Guest
Compare behavior to policy:
If policy is “force guest DNS,” direct queries should be blocked.
If policy allows direct DNS, document the rationale and monitoring.
Pass condition
Matches your intended security policy; no accidental open DNS paths.
C3 — DNS abuse tolerance (lightweight, non-disruptive)
Procedure
Generate controlled bursts of DNS queries from a test client (within safe bounds)
Validate:
resolver logs capture spikes
alerts exist for sustained abnormal rates
Standards-based guidance NIST SP 800-81 provides DNS deployment security guidance that supports hardening and resilience principles.
6) Test suite D — Portal and certificate trust validation
D1 — TLS trust and SAN alignment
Procedure
Access portal FQDN from Guest
Validate certificate trust:
no warnings
correct SAN/CN alignment
Pass condition
Portal is trusted by default on unmanaged clients (reduces phishing enablement)
D2 — Redirect chain hygiene
Procedure
Inspect captive portal redirect chain
Ensure it does not expose:
internal hostnames
internal IPs
sensitive query parameters
Pass condition
Redirect chain uses public/guest-safe names only.
7) Test suite E — DoS resilience (basic assurances)
Do not run disruptive tests in production without approvals. The goal is sanity checks.
E1 — DHCP lease stress (safe, limited)
Procedure
Perform a limited number of reconnects/renewals from test clients
Watch DHCP pool utilization and logs
Pass condition
DHCP remains stable; pool not easily exhausted by trivial behavior
E2 — Association/auth spikes (monitoring proof)
Procedure
Connect/disconnect in controlled bursts
Confirm monitoring/alerts detect unusual behavior
MITRE correlation Network Denial of Service (T1498).
8) Evidence collection (what to store as proof)
For each validation run, capture:
timestamp, location, SSID, VLAN/VRF, policy version
test results table (pass/fail)
packet capture excerpts (where safe)
firewall logs/denies summary
DNS query logs summary
screenshots for portal TLS proof
This becomes your “security acceptance package” for Guest.
9) Continuous assurance (make it sustainable)
A secure Guest design decays over time due to:
new exceptions
vendor upgrades
topology changes
portal/cert renewals
DNS changes
Recommendation
Run this validation:
after any change
after upgrades
periodically (e.g., quarterly)
Treat failures as a security defect.
Appendix — Quick mapping to MITRE ATT&CK
Discovery: Network Service Discovery (T1046)
AiTM: Adversary-in-the-Middle (T1557)
Impact: Network Denial of Service (T1498)
For “kill chain” methodology references, see Lockheed Martin Cyber Kill Chain resources.
