Build an 802.1X lab

These hands-on guides walk a complete 802.1X deployment on a lab small enough to build in an afternoon, and concrete enough that every command and every checkbox is one you will actually type. This first page builds the foundation the others start from: a switch that talks RADIUS to Taranac, one access port under 802.1X, and a Windows PC on the other end of the cable.

Nothing here authenticates a user yet — that is deliberate. The single most common way an 802.1X rollout stalls is that the plumbing was never proven before the supplicant was touched, so a switch-side problem gets mistaken for a client problem for hours. By the end of this page you will have positive proof that a RADIUS request leaves the switch and arrives at Taranac, and only then do the later guides configure the client.

What you’ll build

Component	Role	Reference address
Taranac	NAC RADIUS server + policy engine	`10.30.0.20`
SW1	Access switch (the authenticator)	`10.30.0.11`
Windows 10/11 PC	802.1X supplicant	DHCP, on SW1 `Gi1/1`
A dumb client (VPC, printer, camera)	MAB endpoint — used by the MAB guide	DHCP, on SW1 `Gi1/0`

VLANs used throughout the series:

VLAN	Purpose	Gateway
1	Switch management + Taranac	`10.30.0.1`
10	Data — where authenticated corporate devices land	`10.30.10.1`
30	Guest / quarantine	`10.30.30.1`
40	Printers and other MAB’d devices	`10.30.40.1`
300	Restricted — what the shipped `MAB-Default` profile assigns	none needed for this page

Substitute your own addressing as you go — the only hard requirement is that the switch and Taranac can reach each other on UDP, and that the switch’s RADIUS source address matches what you register in Taranac.

Before you start

Taranac installed and reachable. See Installation or the virtual appliance. You need admin access to the web UI.
A switch with a management IP and an L3 path to Taranac. Console or out-of-band access to that switch — you are about to enable port authentication, and locking yourself out of a lab switch is a rite of passage worth skipping.
A Windows 10/11 machine with a wired NIC on a port of that switch.
The NAC RADIUS ports open between them: auth 1814/udp, accounting 1815/udp, CoA 3799/udp.

Step 1 — Register the switch in Taranac

A switch that is not registered is not a client: the NAC server drops its packets before any policy runs, and you will see nothing in the logs. This step comes first for that reason.

Open Infrastructure → Network → Devices (/network/devices) and click Add Device.
Fill in the identity side — a name, and a Network Object carrying the switch’s address (a /32 host object is the usual choice). That address must be the one the switch sources RADIUS packets from, not necessarily its loopback or its DNS name. Vendor and Platform are optional but worth filling in — vendor is what CoA encoding auto-detects from later. Since 1.2.8 the form also carries a Device Groups picker, so membership no longer has to be written from the group’s side; a one-switch lab can leave it empty.
Under Protocol Support, turn on NAC. NAC rides on the RADIUS protocol, so enabling it reveals the RADIUS Secret field even when the RADIUS toggle itself is off — that same secret is what your radius server line on the switch must carry. Set a strong one and keep it to hand.
Leave CoA Port empty — empty means inherit, the device falls back to its group and then to the global nac.coa_port, which ships as 3799. The Details panel on the right spells out what is actually in effect, and will read 3799 (Global default).

Set the CoA Secret, though. It inherits the same way, but the global nac.coa_secret is a random 32-character value Taranac generates on first start — nothing you have ever typed on a switch. Leave the field empty and Taranac will sign every reauth, bounce and VLAN change with a secret the switch cannot verify, so CoA silently fails while authentication keeps working. Put the same value here that you put on the switch’s CoA listener in Step 2 (the lab reuses the RADIUS secret for both). If you would rather use the generated global one, reveal it under NAC → Settings → NAC (/nac/settings) and paste that into the switch instead — the reveal is audit-logged.
Optionally pin a Vendor Dictionary (CoA). Left empty, Taranac detects the vendor and falls back to a generic encoding; set explicitly, CoA actions (reauth, bounce, VLAN change) are encoded exactly the way that platform expects.
Press Create Device.

Device edit form: protocol toggles with NAC on, the RADIUS secret, and the NAC CoA settings The device form. RADIUS is off and the RADIUS Secret field is still there — that is NAC reusing it. On the right, the Details panel resolves what each setting actually evaluates to, including 3799 (Global default) for the CoA port left blank on the left.

Secrets resolve along a three-level chain — device → device group → global setting — with the first level that has a value winning. For a lab, set it on the device. For a real network, a per-site device group carrying the secret is usually the better shape; see Network devices.

Step 2 — Point the switch at Taranac

Now the switch side. This block is global plumbing only: which server, which ports, which secret, and the master switch that turns 802.1X on.

Cisco IOS
Arista EOS

! ── The NAC RADIUS server ───────────────────────────────────────
radius server TARANAC-NAC
 address ipv4 10.30.0.20 auth-port 1814 acct-port 1815
 timeout 5
 retransmit 2
 key <RADIUS_SECRET>

! ── Its own server group, so device-admin AAA is untouched ──────
aaa group server radius TARANAC-NAC-GRP
 server name TARANAC-NAC
 ip radius source-interface Vlan1

aaa authentication dot1x default group TARANAC-NAC-GRP
aaa authorization network default group TARANAC-NAC-GRP
aaa accounting dot1x default start-stop group TARANAC-NAC-GRP

! ── The global 802.1X master switch ─────────────────────────────
dot1x system-auth-control

! ── Source + attributes ─────────────────────────────────────────
ip radius source-interface Vlan1
radius-server attribute 6 on-for-login-auth
radius-server attribute 8 include-in-access-req
radius-server attribute 25 access-request include

! ── CoA listener (Taranac pushes reauth / disconnect here) ──────
aaa server radius dynamic-author
 client 10.30.0.20 server-key <RADIUS_SECRET>
 port 3799
 auth-type any

! ── The global 802.1X master switch ─────────────────────────────
dot1x system-auth-control
dot1x dynamic-authorization

! ── The NAC RADIUS server + CoA listener ────────────────────────
radius-server host 10.30.0.20 auth-port 1814 acct-port 1815 key 0 <RADIUS_SECRET>
radius-server dynamic-authorization port 3799

aaa group server radius TARANAC-NAC
 server 10.30.0.20 auth-port 1814 acct-port 1815

aaa authentication dot1x default group TARANAC-NAC
aaa accounting dot1x default start-stop group TARANAC-NAC

On EOS the CoA key comes from the radius-server host line — there is no separate client/server-key stanza like Cisco’s aaa server radius dynamic-author, and EOS will reject that syntax if you try to paste it. Write the key as key <RADIUS_SECRET> or key 0 <RADIUS_SECRET>; the key 7 … form is the obfuscated spelling the switch prints back in show running-config, not something you type.

Three EOS specifics are worth stating plainly, because all three fail quietly:

The server group holds a copy of the address and ports, not a reference to the radius-server host line. The two lines above happen to agree — keep them agreeing. aaa authentication dot1x default group TARANAC-NAC resolves through the group, so a group entry left pointing at the old ports sends every 802.1X and MAB request to a port nothing is listening on. There is no timeout to watch and no reject to read: Taranac’s NAC log shows no event at all, which reads as a broken supplicant. That trap and its fix are on Arista EOS — we lost six days to it in this very lab after moving the NAC ports.
CoA needs two lines, not one. radius-server dynamic-authorization port 3799 opens the listener; dot1x dynamic-authorization lets the dot1x process apply what arrives. They are independent, and having only the second one is a config that looks CoA-ready and silently drops every reauth/disconnect Taranac sends. Nothing about authentication breaks, so this can sit unnoticed indefinitely.

Verify it by behaviour, not by reading the config: with the port left at its default, the listener line may not appear in show running-config at all, since EOS omits values that match defaults. Use show running-config all and show radius to confirm it is really there — and re-check after a reload, so a setting that was only ever applied at runtime does not quietly disappear on the next reboot.
Accounting is its own line, and sessions depend on it. aaa accounting dot1x is what produces the Accounting-Requests that create sessions in Taranac. A switch missing it authenticates perfectly and shows up in the auth log while producing zero sessions.

Two more things worth getting right the first time:

Source the RADIUS packets deliberately. ip radius source-interface Vlan1 (Cisco) makes packets carry the switch’s management IP, which is what you registered in Step 1. If the source address and the registered address disagree, the NAC server sees an unknown client and drops the request without logging a policy decision.
The secret is per device. It must match the radius_secret on this switch’s device entry. Not the TACACS+ key, and not another switch’s secret. A mismatch surfaces as a rejected or unanswered request at the NAC handler.
Save the configuration — write memory on Cisco, write on EOS. A lab switch that reloads with half of this config missing produces symptoms that look nothing like “the config is gone”: authentication may keep working while accounting silently stops, so sessions vanish from Taranac while access still succeeds.

Step 3 — Configure the access port

Wire the Windows PC to Gi1/1 and apply the port config. This is a dot1x port with MAB as the fallback — the shape you will use for most real access ports.

Cisco IOS
Arista EOS

interface GigabitEthernet1/1
 switchport access vlan 10
 switchport mode access
 ip device tracking maximum 10
 authentication open                       ! ← monitor mode; remove when you go live
 authentication order mab dot1x
 authentication priority dot1x mab
 authentication port-control auto
 authentication periodic
 authentication timer reauthenticate server
 authentication violation restrict
 mab
 dot1x pae authenticator
 dot1x timeout tx-period 10
 spanning-tree portfast edge

authentication order sets which method is tried first; authentication priority sets which one wins if both could succeed. Ordering MAB first and prioritising dot1x is the usual pairing: a device that never sends EAPOL gets MAB’d quickly, while a real supplicant still ends up authenticated by 802.1X.

interface Ethernet3
 switchport access vlan 10
 switchport mode access
 dot1x pae authenticator
 dot1x port-control auto
 dot1x host-mode multi-host authenticated
 dot1x reauthentication
 dot1x mac based authentication
 dot1x timeout tx-period 10
 spanning-tree portfast edge

On EOS, MAB is dot1x mac based authentication on the port. With both enabled, 802.1X is attempted first and MAC-based authentication is the fallback. EOS has no direct equivalent of Cisco’s authentication open, so keep console or out-of-band access to the switch while you bring the port up.

Step 4 — Prove the plumbing before touching the PC

Do not configure the Windows supplicant yet. First confirm that a request physically reaches Taranac.

On the switch:

Cisco IOS
Arista EOS

show dot1x
show dot1x interface GigabitEthernet1/1 details
show authentication sessions interface GigabitEthernet1/1 details
show aaa servers

show dot1x must report that 802.1X is enabled system-wide. If it does not, you skipped dot1x system-auth-control.

show dot1x
show dot1x interface Ethernet3
show radius
show aaa accounting
show mac address-table
show logging

show radius should list the Taranac server and the dynamic-authorization listener; if the listener is absent, you have dot1x dynamic-authorization without radius-server dynamic-authorization port 3799. Note that the listener line may be missing from show running-config even when it is active — check show running-config all before concluding anything from the config text. show aaa accounting must show a dot1x method pointed at your server group — without it you will authenticate but never create a session.

On Taranac: open Logging & Reports → NAC Logs → Auth Log (/logging/nac/authentication). Plug the PC in, or bounce the port (shutdown / no shutdown), and watch.

With Windows’ 802.1X not yet configured, the PC sends no EAPOL, so the port authenticates it by MAB — using the PC’s MAC address as the identity. On the Cisco config above that happens almost at once, because authentication order mab dot1x tries MAB first; on EOS 802.1X runs first and MAB takes over once the dot1x timeout tx-period 10 retries have run out. Either way, a MAB row for the PC’s MAC appears in the log.
That row will say accept, not reject — and the accept is the result to expect. What proves this step is that a request arrived and was decided: the row exists at all, it names your switch, and it names a rule. The verdict itself is the seeded policy talking, not your lab (see the callout below).
The device should also appear under NAC → Endpoints → Endpoints (/nac/endpoints), auto-discovered from the MAC the switch reported, with status unknown and its vendor filled in from the OUI database.

It is tempting to read a first accept as “already working” or a first reject as “still broken”. Neither is what is happening. A fresh install seeds three policy rules, evaluated strictly first-match-wins:

#	Rule	Matches	Result
1	`Dot1x Known Users → Corporate`	PEAP · any user · any endpoint · any device · always	permit → `Corp-Default` (VLAN 100)
2	`MAB Known Endpoints → Restricted`	MAB · any · any · any · always	permit → `MAB-Default` (VLAN 300)
—	`Default — Reject`	everything else	reject

Rule 2’s name says known endpoints, but its conditions are all any: the endpoint Taranac just auto-discovered matches it, and the answer is an Access-Accept carrying VLAN 300. So your unconfigured Windows PC is admitted to the Restricted VLAN, by a rule you did not write, before you have configured a single thing about identity. That is why the VLAN 300 note near the top of this page matters — and why the PEAP guide starts by putting its own rule above rule 1.

Three things follow for the rest of the series:

The Default — Reject catch-all is not reached by 802.1X or MAB on a fresh install. Anything you want denied has to be denied by a rule of yours sitting above these two, or by disabling them.
The policy table’s Add rule button appends the new rule before the default rule — i.e. below both catch-alls, where it will never be reached. Use the ↑ Insert rule above control on the row you want to precede instead — the drawer then opens titled New rule at position #N. The PEAP guide walks it.
Re-authenticate once before believing a verdict on a brand-new MAC. In our own lab a first MAB from a never-seen endpoint landed on this catch-all and only the second attempt matched the rule that was written for it. Bounce the port and read the second row.

If nothing arrives at all — or something arrives and misbehaves — work down this table before changing anything on the client.

Symptom	Likely cause	Fix
No requests reach Taranac at all; port is silent	`dot1x system-auth-control` missing	Add it globally — see the callout above
Nothing in the NAC log, but device-admin logins work	Switch pointed at `1812`/`1813`	NAC listens on `1814`/`1815`
Nothing in the NAC log, the switch says the server is dead	Source IP ≠ registered device IP	An unregistered source is not a RADIUS client, and FreeRADIUS discards the packet before anything is logged — there is no “unknown client” row to find. Set `ip radius source-interface`, or correct the device’s Network Object
Nothing in the NAC log, Arista switch, config looks right	Stale server copy inside `aaa group server radius`	The group holds a copy of the ports, not a reference. Compare it against the `radius-server host` line — see Arista EOS
Access-Reject, secret suspected	Wrong or stale shared secret	The secret must equal this device’s RADIUS secret, not the TACACS+ key and not another switch’s
Device saved in Taranac but still not a client	Config not regenerated yet	Wait ~30 s (`nac.auto_reload_interval`), then retry
CoA sent but the session never changes	The CoA secret does not match	Taranac signs CoA with device → group → global `nac.coa_secret`, and the global one is randomly generated. Set it on the device, matching the switch’s listener — Step 1
CoA sent but the session never changes	CoA listener points elsewhere	The switch’s `client` / listener must name the Taranac that serves this switch, on the resolved port

What’s next

The lab is now a working NAC testbed: the switch asks, Taranac answers, and every answer is logged. From here:

802.1X with PEAP — create a user, build a policy that gets in front of the seeded rules, configure the Windows supplicant window by window, watch a real authentication succeed, and close the port.
EAP-TLS for domain users — certificates instead of passwords, for Active Directory accounts.
Machine authentication and SSO — the computer authenticates at boot, the user at logon, and the policy order that decides which one wins.
EAP-TTLS for directory users — a directory password inside a TLS tunnel, with no NT hash stored anywhere.
MAB for printers and IoT — take the dumb client on Gi1/0 from unknown to classified and onto a VLAN you chose rather than the seeded MAB-Default. (Coming next in this series.)

NAC overview — how the pieces fit together
Network devices — device fields, groups and secret inheritance
802.1X authentication — what each EAP method needs
NAC policy — authorization profiles and rule matching