C1117 Unable to push image.

[Sumit Sharma]

Hi All, Need assistance  w.r.t to issue with the enterprise network.

An enterprise network has a C1117 ISR running on 4G (only WAN). Role of the router is to provide connectivity between the controllers and centralized server for the controllers (in data center). 

Routing seems ok, no acl blocking any thing though the controllers is not downloading latest image.

What could be the issue? 

[Leo Laohoo]

Is the router running SD-WAN image?

[Sumit Sharma]

Hey Leo, nope. Not SD WAN.

Just to be clear the controller connected to the router are not able to Download the image.

[Leo Laohoo]

What controller?
What if the "image" is published locally?

[Sumit Sharma]

Controllers/servers to manage building security (not managed by me). Am just thinking of all possible options. The controllers/server can communicate to the Centralised server but not able to download the image on to the controller. Not sure what is the issue.

[Leo Laohoo]

Firewall?

[Sumit Sharma]

Port is open, we can even telnet 

[Leo Laohoo]

A client behind the router is trying to upload or download a file?
How big is this file?

[Sumit Sharma]

Client is downloading the latest image. Size am not sure.

[Sumit Sharma]

Issue seems to be with the MSS value tough I have trouble in determining the MSS size for C1117 router with 4G carriage to solve an issue. 

Currently we have MSS set as 1310 and MTU as 1455 on the Cellular interface. We are running IPSEC GETVPN to encrypt the data between the router and aggregate router in DC.

I performed the Ping sweep test with DF set which stops at 1283 bytes.   Min Bytes = 1250, max Bytes = 1310 

could any one be able to confirm if 1282 bytes is the payload + 20 bytes IP + 20 bytes TCP header summing up to MSS as 1312 bytes or MSS is 1282 bytes?