Controller-less WLANs

Problem:

Will IAPs configured with static IP address switch to get IP address from DHCP?

The answer is 'Yes'. As per our requirement we can either have Instant APs assigned with static IP address or configure them to get IP address from DHCP server. However if these APs are configured with "internet failover" and "preemption" enabled in their uplink configuration then the APs would switch from static assignment to DHCP assignment and try to get IP address from DHCP server.

Let us see with an example of how this option impacts in a real time scenario:

1. Have an Instant AP configured with static IP address.

ArubaOS (MODEL: 335), Version 6.5.4.5

Website: http://www.arubanetworks.com

(c) Copyright 2018 Hewlett Packard Enterprise Development LP.

Compiled on 2018-02-10 at 14:39:17 UTC (build 63641) by p4build

FIPS Mode :disabled

AP uptime is 15 weeks 3 hours 18 minutes 5 seconds

Reboot Time and Cause: AP rebooted due to loss power

=======================================================================


Aruba# show ap-env      ---------> Static parameters configured

Antenna Type:Internal

Need USB field:Yes

name:Aruba

ipaddr:10.2.16.10

netmask:255.255.0.0

gatewayip:10.2.0.254

dnsip:10.2.0.156


Wired Interface     

----------------

mac                                ip         gw-ip             gw-mac          status         pkts      macs  gw-macs  dot1q-pkts  vlans

---                                   --           -----                  ------             ------            ----        ----        -------        ----------     -----

a8:bd:27:c5:c9:26       10.2.8.22  10.2.0.254  c0:67:af:93:89:41  enable  57382051  258           1                  0           0          


Master IP Address    :10.2.16.2

IP Address           :10.2.8.22

Netmask              :255.255.0.0

Gateway              :10.2.0.254

=======================================================================

• From the above log, we can find the IAP with 10.2.8.22 IP address was able to find the Master with IP- 10.2.16.2 in the same subnet.
• However from the system logs we can see the trigger happened to switch IP address from static IP to DHCP

Aruba# show log system

Sep 13 00:22:44  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  arping ongoing for central rollback

Sep 13 00:23:47  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  arping ongoing for central rollback

Sep 13 00:24:03  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  Send awc hang detection.

Sep 13 00:24:03  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  Recv awc hang reply.

Sep 13 00:24:06  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  arping ongoing for central rollback

Sep 13 00:24:39  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  arping ongoing for central rollback

Sep 13 00:29:05  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  Send awc hang detection.

Sep 13 00:29:05  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  Recv awc hang reply.

Sep 13 00:29:08  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  arping ongoing for central rollback

Sep 13 00:29:41  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  arping ongoing for central rollback

Sep 13 00:30:44  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  arping ongoing for central rollback

Sep 13 00:31:24  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  dhcp probe sucessfully for cloud recovery

Sep 13 00:31:26  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  cloud failure trigger staticip to DHCP switch.

Sep 13 00:31:26  cli[2921]: <341185> <WARN> |AP Aruba@10.2.16.10 cli|  Retrieving ip address from br0, ip 10.2.8.22, mask 255.255.0.0.

Sep 13 00:31:26  cli[2921]: <341274> <WARN> |AP Aruba@10.2.16.10 cli|  Update election ip from br0, election ip 10.2.8.22/255.255.0.0.

Sep 13 00:31:26  cli[2921]: <341004> <WARN> |AP Aruba@10.2.16.10 cli|  build_my_ip_address:setting this as new IP address for swarm

=======================================================================

• From system logs, we can find the connection to cloud failed by 00:31:26 which triggered to switch Static IP to DHCP
• This is due to the fact that when "internet failover" and "preemption" is enabled in the uplink configuration the AP will switch from static IP to DHCP when the primary uplink fails.
• In this scenario the connectivity to the Aruba Central fails and so the AP tries to get IP address from DHCP server.

===========================================

Aruba# show uplink config

Uplink preemption             :enable

Uplink preemption interval    :600

Uplink enforce                :none

Ethernet uplink eth0        :DHCP

Internet failover             :enable

Max allowed test packet loss  :10

Secs between test packets     :30

VPN failover timeout (secs)   :180

Internet check timeout (secs) :10

===========================================

This change from static to DHCP is expected when those two knobs are enabled but this would cause a network down scenario when we are managing Instant APs with Static IP address. To overcome this situation either we need to have IP address assigned through DHCP for APs or disable "internet failover" and "preemption" from the uplink configuration.

Aruba# show uplink config

Uplink preemption             :disable

Uplink preemption interval    :600

Uplink enforce                :none

Ethernet uplink eth0        :DHCP

Internet failover             :disable

Max allowed test packet loss  :10

Secs between test packets     :30

VPN failover timeout (secs)   :180

Internet check timeout (secs) :10