Sure Signal stopped working after upgrade to BT Infinity

[JonasBrown]

Hi

Howe recently up graded our broadband and since this time the sure signal has stopped working, no lights at all. I we reset the lights do flash etc so power is not the issue.

I also keep receiving texts saying we have moved the unit and need to update the postcode, though it hasn't in fact moved.

any suggestions?

[Jimfew]

I had some minor instability on my wireless connection becuase of my unusual setup. On my Laptop I have both a Dual band Linksys adapter working on the N band at 2.4GHz and another Netgear adapter working on the AC band at 5GHz. I did this to compare the two types on wireless interface. As an aside, the new AC band is really, really fast. The two adapters confused the ASUS router until I did a firmware update. Now they work fine together. One minor quirk is that I had to disallow access for my AC adapter on the 2.4GHz band but I did this using the MAC address filter which is separate on the ASUS for both the 2.4 and 5GHz bands. What a seriously great piece of kit that ASUS is!

Jim.

[Ben_H]

Hi connectcctv,

As this is a router issue, are BT not able to advise you further or supply you with a router that allows the 1500 MTU? If not then I'm afraid we're a little restricted in what else we can suggest for your case as we're trained and certified to support our hardware, not the many thousands of different routers out there.

Cheers, Ben

[Jimfew]

I had this problem. If you search for a thread by me about BT Infinity it will give you some ideas. What router make and model do you have?

I suspect your problem is to do with MTU threshold. The VSS sends out packets with an MTU of 1500 but the BT Infinity fibre network works on PPPoE at a MTU of 1492. That means that the packets from the SS need to be fragmented in order to properly pass through the infinity network. Some routers can handle this, some need some fettling to do this and others will not. One particular problem is that the packets from the VSS have the "do no fragment" bit set in their header. Your router must be able to ignore this and fragment anyway.

If you use the standard BT insued router for their Infinity service then, people say, it would normally work OK as it fragments the packets whatever the MTU. I use a Draytek 2820 Router and have set the DF_enable flag to ON. It works fine as it just ignores the do not fragment flag bit and fragments the packets anyway.

Jim.