Hello Friends,

I am working on configuring cEdge router model ISR 4331 in my ongoing project for a client. I created a sub-interface with the following configuration on main interface and its sub-interface but when I commit it gives error

Aborted: 'vpn 1 interface GigabitEthernet1/1/0.33 mtu': Tagged interface MTU needs to be at least 4 bytes less than parent interface (GigabitEthernet1/1/0) mtu (1504)

Configure on Interface and Sub-Interface

!

interface GigabitEthernet1/1/0
mtu 1504
no ip address
no ip redirects
load-interval 30
negotiation auto
arp timeout 1200
!
interface GigabitEthernet1/1/0.33
encapsulation dot1Q 33
vrf forwarding 1
ip address 192.33.106.1 255.255.255.252
no ip redirects
ip mtu 1500
ip nbar protocol-discovery
arp timeout 1200

!

I am sure why this error is appearing, please help.

Regards,

Sanjay

Hi Sanjay - This issue seems to be related to MTU, I think you configure IP MTU on the sub-interface to be 1496, 4 bytes are consumed for additional vlan tagging in this case you have configured sub-interface 33 .

This is a bug which is impacting cEdge routers including ISR 4331

Bug ID: CSCvu33358 

Description: SD-WAN cEdge routers MTU issue in IOS config

you can check the details on Cisco website, this bug is not hitting vEdge routers.

Thanks for your response!! I will explore more on this bug