MACSec Redux


Good ol’ MACSec.

First, I posted a quick and dirty notes-for-myself, MACSec how-to for Juniper.

Then, I posted a similar MACSec howto for Cisco. So here’s a miscellany of different macsec implementations.

Let’s say you want to run your own router, because your Layer 8 & 9 specialists mandate it, here MACSec on linux.

Here’s a guy who did cisco-switch-to-cisco-switch macsec over an mpls link between a cisco and juniper router (because macsec works at layer 1 and thus you need to fake layer 1 via MLPS). So that’s a thing.

Here’s the Extreme Network’s MACSec implementation:

set macsec port mka enable tg.1.1
set macsec pre-shared-key port tg.1.1 ckn foo cak passphrase bar

HP switches macsec config

Brocade MACSec details and also a Brocade sample config of MACSec.

Cisco MACSec Notes


A while back I did notes for MACSec on Juniper devices and here’s the Cisco equivalent of the 802.1AE (“MAC Sec”) implementation

  1. Your Cisco device needs to be running either an IP Base or IP Services image. MACSec is not happening otherwise.
  2. switch# cts credentials id trustsec password mypassword
  3. en then, conf t, then int Gig1/1 (or whatever)
  4. switch(config-if)# cts man
    % Enabling macsec on Gi1/1 (may take a few seconds)…
    switch(config-if-cts-manual)#no propagate sgt
    switch(config-if-cts-manual)#sap pmk abc123 mode-list gcm-encrypt
    switch(config-if-cts-manual)#no shut

Where abc123 is your shared secret. I believe this is analogous to Juniper’s cak. You can do this to aggregated links (“port-channel” for you Cisco folks) but you have to do it before you aggregate the trunks together into a single logical interface. E.g., do this on Gig1/1 and Gig1/2 and then create int Port-channel1 (channel-group 1 mode on in the interface config)


mode-list options are:

  • gcm-encrypt (authentication and encryption)
  • gmac (auth, no encrypt)
  • null (encapsulation only; no auth, no encryption)



  • to use 802.1x (cts dot1x) as opposed to cts man above, you have to enable 802.1x globally on each device.
  • if you select gcm as the sap mode, you need an additional macsec license from cisco (as well as the ipbase or ipservices image/license). if you select gcm without the license, the interface goes into link-down state.


show cts credentials

show macsec summary

show macsec interface

show authentication sessions interface gigabitethernet1/1


Additional reading:

The actual Cisco doc (this is for a cat4500 but translates well most places) (here’s one for 3750/3560)


Automatically reverting configuration mistakes in JunOS and IOS


The old joke goes: I don’t make mistakes. I thought I did once, but I was wrong.

But here’s how to save yourself from mistakes when configuring a JunOS or IOS device:

JUNOS is easy, “commit check”, “commit confirmed” and the handy “rollback”. Frankly, if you’re on a JUNOS device, you should already know about these.

But how to do the same on IOS? Cisco’s configurations happen as soon as you hit enter on the config, right?

Here’s how:

  • The brute force method: “reload in 5”. Write your proposed changes in notepad++ (or notepad.exe if you insist). Login to the device that you’re going to change, and before you do any of your changes, run “reload in 5”. Then, make your changes. If you did something boneheaded that will disable the device or your connection to it, the device will reload from it’s start-config in 5 minutes, effectively erasing your running-config.

Of course, if this is a shared device, you’ve taken everyone offline for the time it takes the device to reboot. Or maybe you don’t want your config saved to start-config as a security measure*. So what do you do in order to prevent a reboot and still maintain the ability to revert a recently made change? Ah, you’ll be wanting the somewhat more sophisticated method 2:

  • First, turn on archive:

cisco-router#configure terminal

then configure a path for where it’ll be stored and save that:

cisco-router(config-archive)#path usbflash0:backup-config
cisco-router#write mem

Now you should be able to use “configure terminal revert time 5” which is IOS’ functional equivalent of JUNOS’ “commit confirmed 5”:

cisco-router#conf t revert time 5

Here it will tell you that your config is being backed up to where you told it to and that the config will be rolled back in 5 minutes. So make your changes:

cisco-router(config)#int gig 0/0

cisco-router(config-if)# shutdown

If everything is good, “configure confirm” to keep the change:

cisco-router(config-if)#configure confirm

For the truly worried, use both methods: “reload in 10” and “revert in 5”. If the revert doesn’t work, the reload will (this will still take down the router, but hey…)

Categories : HowTo  Networking  Security

Juniper MACSec Notes


MACSec is kind of neat (TL;DR for the impatient: layer-1 crypto on links).

Media Access Control Security (MACsec) is an industry-standard security technology that provides secure communication for all traffic on Ethernet links. MACsec provides point-to-point security on Ethernet links between directly connected nodes and is capable of identifying and preventing most security threats, including denial of service, intrusion, man-in-the-middle, masquerading, passive wiretapping, and playback attacks. MACsec is standardized in IEEE 802.1AE.

MACsec allows you to secure an Ethernet link for almost all traffic, including frames from the Link Layer Discovery Protocol (LLDP), Link Aggregation Control Protocol (LACP), Dynamic Host Configuration Protocol (DHCP), Address Resolution Protocol (ARP), and other protocols that are not typically secured on an Ethernet link because of limitations with other security solutions. MACsec can be used in combination with other security protocols such as IP Security (IPsec) and Secure Sockets Layer (SSL) to provide end-to-end network security.

CLI config:

#create an association:
set security macsec connectivity-association ca1

#choose a mode (static cak recommended — see here for why)
set security macsec connectivity-association ca1 security-mode static-cak

#ckn needs to be a 64-digit number in hex, but any empty space is padded w/ 0’s
set security macsec connectivity-association ca1 pre-shared-key ckn deadbeef99

#cak needs to be a 32-digit number in hex, but any empty space is padded w/ 0’s
set security macsec connectivity-association ca1 pre-shared-key cak deadbeef11

# set to 255 to make it “less likely” to be chosen as key server, 0 for “more likely”
set security macsec connectivity-association ca1 mka key-server-priority 0

# set to 6000 for high-traffic environment. default to 2000.
set security macsec connectivity-association ca1 mka transmit-interval 6000

#this leaves headers unencrypted for troubleshooting, set to 0 for full encryption, set to 50 for unencrypted ipv6 headers
set security macsec connectivity-association ca1 offset 30

# replay protection, set to 0 to enforce all packets coming in order
set security macsec connectivity-association ca1 replay-protect replay-window-size 5

# exclude a protocol
set exclude-protocol lldp

#enable macsec
set security macsec interfaces xe-0/1/0 connectivity-association ca1

show security macsec statistics interface xe-0/1/0 detail

additional reading:
(Cisco version:


There’s a Cisco version of this here:

Categories : HowTo  Networking  Security

Domain Authentication against AD for Cisco and Juniper network devices


On the AD side:

  1. Install NPS on your AD DC.
  2. Create a key ( has screenshots, if you need that sort of thing.)
  3. add clients (your switches/firewalls)

See also

On a Cisco ASA:

aaa-server RADIUS protocol radius
aaa-server RADIUS host [IP address of your RADIUS box / AD machine running NPS] key [key]
radius-common-pw [key]
aaa authentication telnet console RADIUS LOCAL
aaa authentication ssh console RADIUS LOCAL
aaa authentication https console RADIUS LOCAL
aaa authentication http console RADIUS LOCAL

On a Cisco switch:

This example shows local authentication, which lets you Telnet into the router with username “cisco” and password “cisco.”

aaa new-model
username cisco password 0 cisco
line vty 0 4
transport input telnet

In order to test authentication with SSH, you have to add to the previous statements in order to enable SSH.

ip domain-name host.domain.tld
crypto key generate rsa
ip ssh time-out 60
ip ssh authentication-retries 2

If you want to prevent non-SSH connections, add the transport input ssh command under the lines to limit the router to SSH connections only.

line vty 0 4
transport input ssh
cry key gen rsa
ip ssh time-out 30
ip ssh version 2
line vty 0 4
transport input ssh


On a Juniper switch or firewall running JunOS:

set system authentication-order [radius password]
set system radius-server [IP Address of DC running NPS] secret [key]
set system radius-server [IP Address of DC running NPS] source-address [IP Address of interface that will communicate to DC]
set system radius-options password-protocol mschap-v2
set system login user [username] full-name "[Full User Name]" uid 9999 class super-user
# NOTE this erases your local password, so that ONLY the Domain password is allowed. This is more secure but more of a PITA if your NPS box craps out.
delete system login user [username] authentication encrypted-password