VSS1 not working with BT Infinity Business Hub 3

[stuarthatto]

VSS1 has been working just fine for many years but switched to BT Infinity on Friday and has not worked since. I have had VF resynch the VSS, resetting it several times, set up port forwarding (even though this wasnt needed previously)

VSS Serial:  1224332243

It seems to me that the MTU is the issue here. From what I can see VSS1 (maybe all VSS) doesnt allow fragmented packets. The business hub has a max MTU setting of 1492, VSS seems to only allow an MTU of 1500 bytes and ignores fragmented packets. I know traffic is being fragmented because the hub is tel;ling me it is:

IN: BLOCK [5] Fragmented packet (IP 212.183.133.179->81.136.222.41 fragment_offset=1480)

stuarts-mbp:~ stuarthatto$ nslookup 212.183.133.179

Server:192.168.0.1

Address:192.168.0.1#53

Non-authoritative answer:

179.133.183.212.in-addr.arpaname = cluster4.vap.vodafone.co.uk.

My Business hub firewall is turned OFF.

It seems that the router is rejecting the packet because the DF bit is set (do not fragment) which of course the router has to do because its max MTU is set to 1492, not 1500.

So, how do I proceed here? There is no option on the BT Business Hub to ignore DF bit and VSS doesnt do MTU path discovery and allow a lower MTU.

Any help would be VERY welcome ...

Stuart

[stuarthatto]

I have spoken at length to BT who have confirmed my router is correctly configured and say the problem is Vodafone sending incorrectly sequenced fragments which are being rejected by the router. So they squarely blame Vodafone.

I spoke today to SureSignal Technical Support who of course blamed BT unreservedly.

So... where do I go from here please?

[Retired-Matt_B]

Hi stuarthatto,

As DaveCD has stated above, we are aware of some issues with the compatibility of our Sure Signal with BT Infinity for Business routers.

We issued a statement on this which I have posted below:

"We’ve become aware that a very limited number of BT infinity for Business routers have difficulties with the Sure Signal device. After lengthy investigations, unfortunately we’ve been unable to rectify the issue. Sure Signal works with the vast majority of broadband routers, but we cannot guarantee its use with every router. We’re very happy to refund Sure Signal devices within the first seven days of purchase."

Thanks,

Matt B

[stuarthatto]

So basically I am stuffed. Both you and BT are blaming each other and your business Customers are left to find their own solution?

It seems the only solution is to move to O2 because at least I have a signal at my place of work, unlike Vodafone.

[DaveCD]

Hi stuarthatto,

Have you tried this on another connection such as at home or a friend or family members?

If the device is the same at another location, it would mean the device is faulty after four years of service.

As this is now out of warranty, a new device can be purchased here.

DaveCD

[stuarthatto]

The device stopped working on the exact same day of the Infinity regrade. I dont believe in coincidences like that, the SureSignal is fine. However....

If it did work on someone elses Infinity where would you lay the blame then if they have the same router? BT right, must be something wrong with my line... you see the problem is, EVERYTHING else in the house, over 25 devices and 10 virtual systems are all working just fine.

The only error messages in the router logs relate to Vodafone communicating TO my Sure Signal - rejected fragments.

The problem is not with BT, the problem I believe is that Vodafone are sending fragmented packets with bad sequence numbers. Next week when I have time, I am going to take packet captures straight off the Openreach modem, I am certain these will show the problem.

[Jenny]

Hi stuarthatto

Please test this on a different connection with a different router as this will help determine if the Sure Signal is faulty.

Thanks,

Jenny

[stuarthatto]

The SureSignal was working reliably right up to the moment the Inifinity regrade occurred, nothing else has changed, The SureSignal is NOT faulty.

I will take packet captures to prove to you this is a fragmentation/MTU issue.

[stuarthatto · Accepted solution]

Vodafone, I owe you a HUGE apology. I could not grovel enough...:smileyembarrassed:

I replaced the BT Business Hub 3 today with a Billion Bipac 8800NL - didn't have to set up any port forwarding at all and the VSS1 connected for the first time in 2 months.

I also didn't change anything MTU-wise - but the thing with the 8800NL is that it replaces both the business hub AND the openreach modem. Presumably because it is doing both jobs it is capable of reassembling the fragments correctly.

For £70 it was a sound investment and clearly better than the pile of junk BT palm off on its customers.

Sorry again,

Stuart