SD-WAN ISSUE

[caoliveira]

guys I have a problem with an ISR-4331 router that I'm creating an environment, when I create the sub interface and I'm going to commit it complains about the MTU

ERROR THAT IS APPEARING vpn 1 interface GigabitEthernet0/0/1.28 mtu': Please configure ip mtu 4 bytes less than parent interface (GigabitEthernet0/0/1) ip mtu (1500)

interface GigabitEthernet0/0/1
mtu 1504 
no ip address
no ip redirects
load-interval 30
negotiation auto
arp timeout 1200
!
interface GigabitEthernet0/0/1.28
encapsulation dot1Q 28
vrf forwarding 1
ip address 10.33.28.1 255.255.255.252
no ip redirects
ip mtu 1500
ip nbar protocol-discovery
arp timeout 1200 

This is the configuration I am tried to include, I can add only the interface configuration, when I try to include the sub interface 
the error shows up

[Flavio Miranda]

Hi

 It seems you hit the bug CSCvu33358

[Kanan Huseynli · Accepted solution]

Hi,

configure ip mtu for subinterface to be 1496.

[caoliveira]

I was allowed to add the MTU 1496, but I still haven't uploaded the router to the environment, I'm going to test it, in the other environments I managed to configure the MTU normally so I think it's a BUG from the box, but thanks for the help

[Kanan Huseynli · Accepted solution]

Additional info: What is interesting is new configuration mode (configuration group and feature profile) even does not require this settings. I have just added subinterface to service-side VPN (without touching parent physical interface) and it is accepted and it works:

Example from CLI:

interface GigabitEthernet2
no ip address
speed 1000
no negotiation auto
!
interface GigabitEthernet2.10
encapsulation dot1Q 10
vrf forwarding 10
ip address 10.1.1.254 255.255.255.0
no ip redirects
arp timeout 1200