MTU configuration on cnPilot Access Point

Products Enterprise Wi-Fi Networks
1

The max MTU supported on cnPilot AP is 1500 Bytes by default, but it can be increased beyond 1500 to meet the requirement for larger frames in the network. Max the MTU on the interface can be configured is up to 1600 bytes.

There are two ways to configure MTU on cnPilot

  1. Passing the MTU value through DHCP option 26
  2. Manually configuring the value through cli access.

You can configure the DHCP server in the network to send the MTU details in DHCP option 26 along with with IP address. Please see the configuration of DHCP option 26 on the cisco L3 switch. AP will receive the IP address and the MTU value in the DHCP offer packet.

Here is the sample configuration on cisco 3650 switch in the lab which act as DHCP server:

!
ip dhcp pool VLAN100
 network 10.110.200.0 255.255.255.192
 default-router 10.110.200.1
 option 60 ascii "Cambium-WiFi-AP"
 domain-name cambiumnetworks.com
 dns-server 10.110.12.110 10.110.12.111
 option 43 ascii 10.110.200.9
 option 26 hex 0640
 lease infinite
!

Stats on cnPilot AP which display the received MTU value learned from the DHCP server.

E410-93F173(config)# show ip dhcp-client-info
VLAN-1:
-------
ip=10.110.200.26
subnet=255.255.255.192
mask=26
router=10.110.200.1
dns=10.110.12.110 10.110.12.111
domain=cambiumnetworks.com
mtu=1600
vendorspecinfo=10.110.200.9
lease=4294967295
serverid=10.110.200.1
vendorclass=Cambium-WiFi-AP
opt53=05

eth0      Link encap:Ethernet  HWaddr 00:04:56:93:F1:73
          UP BROADCAST RUNNING MULTICAST MTU:1600 Metric:1
          RX packets:13307 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2367 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1108769 (1.0 MiB)  TX bytes:228072 (222.7 KiB)

Alternatively, the user can also ssh to AP and configure the MTU on the vlan interface manually. The cli command to configure is below.

E410-93F173(config)# interface vlan 1
E410-93F173(config-vlan-1)# mtu <1400-1600 bytes>

NOTE: In the case of the Manual configuration of MTU through CLI , the IP address on the VLAN interface should also be static configured.

The support for MTU cli is added from 3.11.3 onwards.

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