Cisco SG550X switch DHCP Snooping & DF (Do not fragment) Issue

[Yasmeen]

Hi Team

         we have one CIsco SG550X switch, when i configured the DHCP Snooping on it. The DF (Fragment is set to as DF =1) 

        In Wireshark Capture its showing as Do NOt Fragment. 

I have one setup as follows 

DHCP Snooping Enabling in SG550X switch  

AP ----> CIsco SG 550 X Switch  ----> TFTP Machine 

set DF =0 ----> changed as DF = 1 -----> Same DF = 1

AP (Access Point) Image UPgarde is not Successful

DHCP Snooping Disabling in SG550X switch  

AP ----> CIsco SG 550 X Switch  ----> TFTP Machine 

set DF =0 ----> changed as DF = 0 -----> Same DF = 0

DF bits sets as 65454

AP (Access Point) Image UPgarde is Successful

I want to enable the DHCP Snooping in cisco SG5550X switch at the same time my Access point Image Upgrade also need to be fine with DF = 0 (65454 bits)

Even though DHCP snooping is disabled, DF bit is set to 1 only..

May be I'm thinking there might be some packet loss when DHCP snooping is enabled. Because of that while doing re-fragmentation at that time it fails

How do i enable both options ?

What configuration needs to be done ?

What are all things happened when DHCP Snooping Enbaled in switch ?

what i need to configure ?

Pls help me to troubleshoot in Cisco Switch 

Thanks in Advance,

Yasmeen Shaul Hameed.

[Georg Pauwen]

Hello,

I don't think there is an option on the SG550x that let's you set the DF bit at all. DHCP snooping is, in theory, completely unrelated.

Which firmware version are you running on the switch > Make sure it is the latest, release 2.5.5.47 (attached in case you don't have it).

[Yasmeen]

Hi georg

                  I have the same Image in my switch. 

#show version
Active-image: flash://system/images/image_tesla_hybrid_2.5.5.47_release_cisco_signed.bin
Version: 2.5.5.47
MD5 Digest: ff7132e875fd9ac0699a4b7bf04087c4
Date: 06-May-2020
Time: 17:32:16

My Issue is, 

my Access point sent the request to TFTP via cisco Switch 

Access Point -----> CIsco SG550X switch ----> TFTP

DF = 0 -------> Changed as DF = 1 -----> 

Automatically my Fragment value as = 1

In switch it's showing as Do not fragment 

I want to transfer the MTU value as 65454 

not with default MTU size - 512, 1024 

Why automatically my DF bit changed as 1 

when i set the value DF = 0 in Access point 

Pls let me know the reason for from AP DF = 0 to SG550x switch DF = 1 changing ?

what i need to configure ?

Thanks in Advance,

Yasmeen Shaul Hameed.