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2850vn dreadful ADSL2+ performance - what have I done wrong?

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08 Nov 2011 18:19 #69982 by irien
Hi folks!

For a long time, we've been using Vigor 2600Vg routers to provide decent ADSL connectivity and Lan to Lan facilities between two family homes.

Today, a new 2850Vn arrived as one of the homes should be able to get 12+Mb on an ADSL2+ exchange (and ultimately benefit from FTTC). The old 2600 was getting a solid 8Mb ADSL1 connection, with typical download speeds of 650-800Kb/s.

Having connected up the 2850Vn in its place (same filters, but I tried replacing the phone cable) the router reports a download sync speed of 14-15 Mbit, which looks promising. "Yay!", I thought.

However, real-world download was *much* lower - initially about 5Mbit (compared to 6.5-8 on the 2600) when using various online speed tests, but subsequently plumeting down to almost old-school modem speeds! BT speedtest reported 5kb/sec download, yet 350 upload!

Clearly this isn't good. I have checked the online status info on the new Vigor (I noticed it didn't have some of the spectrum analysis diagnostics that existed on the 2600) and I noticed that the Rx CRC errors are very high - 25,367 right now, after 30mins of uptime. 26,000 now. 26,500... as I type. You get the idea. This seems very wrong indeed. Also, the SNR Margin is reported as 3 right now, but sometimes 2. Loop Attenuation is 30.

My ISP is plusnet, and I'm using 0/38 VCP/VPI settings. I disabled the 0/101 bridge that was auto-created.

Any thoughts gratefully received!

Thanks in advance,

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12 Nov 2011 17:20 #70041 by cbsys
You should speak to your ISP and get them to do a diagnostics on your line

The 25,367 errors suggest there is a problem with your telephone line, as a result your BRAS profile (the setting which determines your data download speed) is low.

Once the fault is fixed, your BRAS profile will go up and you'll start to see downloads closer to your sync speed!

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