Problem:When Aruba AP is connected to switch port it reports giant packets Rx on the interface.
Diagnostics:MTU on the switch is set to default for AP Vlan which is 1522.
Verified MTU on Aruba AP under ap system-profile which is left at default as below,
(host) #show ap system-profile default
AP system profile "default"
---------------------------
Parameter Value
--------- -----
RF Band g
RF Band for AM mode scanning all
Native VLAN ID 10
Tunnel Heartbeat Interval 1
Session ACL ap-acl
Corporate DNS Domain N/A
SNMP sysContact N/A
LED operating mode (11n/11ac APs only) normal
LED override Disabled
Driver log level warnings
Console log level emergencies
SAP MTU N/A
RAP MTU 1200 bytes
LMS IP N/A
Backup LMS IP N/A
LMS IPv6 N/A
Backup LMS IPv6 N/A
LMS Preemption Disabled
LMS Hold-down Period 600 sec
LMS ping interval 20
Remote-AP DHCP Server VLAN N/A
Remote-AP DHCP Server Id 10.10.10.1
Remote-AP DHCP Default Router 10.10.10.2
Remote-AP DHCP DNS Server N/A
Remote-AP DHCP Pool Start 192.168.1.1
Remote-AP DHCP Pool End 192.168.1.50
Remote-AP DHCP Pool Netmask 255.255.255.0
Remote-AP DHCP Lease Time 0 days
Remote-AP uplink total bandwidth 0 kbps
Remote-AP bw reservation 1 N/A
Remote-AP bw reservation 2 N/A
Remote-AP bw reservation 3 N/A
Remote-AP Local Network Access Disabled
IPM activation Enabled
IPM power reduction steps with priorities disable_usb/priority:2
IPM power reduction steps with priorities cpu_throttle_25/priority:1
Bootstrap threshold 8
Double Encrypt Disabled
Dump Server N/A
Heartbeat DSCP 0
Management DSCP N/A
IP DSCP to VLAN 802.1p priority mapping N/A
Maintenance Mode Disabled
Maximum Request Retries 10
Request Retry Interval 10 sec
Number of IPSEC retries 85
Secondary Master IP/FQDN exit
AeroScout RTLS Server N/A
RTLS Server configuration N/A
RTLS Server Compatibility Mode Enabled
Slow Timer Recovery by rebooting itself Disabled
Telnet Enabled
Disable RAP Tftp Image Upgrade Disabled
Spanning Tree Enabled
AP multicast aggregation Disabled
AP ARP attack protection Enabled
AP multicast aggregation allowed VLANs none
Console enable Enabled
AP Console Protection Disabled
AP Console Password ********
Password for Backup ********
AP USB Power override Disabled
RF Band for Backup all
Operation for Backup off
BLE Endpoint URL N/A
BLE Auth Token N/A
BLE Operation Mode Disabled
Health Check Disabled
Health Check Parameter mode ping packet-size 32 burst-size 5 report 60 frequency 10 retries 3
AirMatch Report Period 5 minutes
AirMatch Measurement Duration 5 minutes
AirMatch Report Enabled Enabled
SAP MTU is used for the wired link of the AP. When this value is not configured, AP sends MTU discovery packet to negotiate the MTU between AP and controller which is also the path MTU. However, at default the SAP MTU value is considered to be 1500 bytes.
When it is configured, AP uses the configured SAP MTU, no more packets to do MTU discovery.
With the above-mentioned settings, the switch port with Aruba AP connected reports incremental Giant packets even though Jumbo is not enabled on switch, AP or controller.
SolutionManually configuring the SAP MTU under ap system-profile of the Access point to 1500, resolves the issue.
If not, the AP tends to continuously do a MTU discovery which results in Giant Rx packets.