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UK BT ADSL2+ Annex A - Cisco 877
UK is currently going through a nationwide migration from ADSL, ADSL2 and ADSL2max to ADSL2+.
Most British Telecom (BT) MSANs are configured for Annex A, though we know that some LLU suppliers are using Annex M (with UK mask) which Cisco currently doesn't support.
Our issues are that all out Cisco 877s and there are 100s deployed that are subject to a line upgrade, or a new installs on ADSL2+ fail.
We have used the latest IOS that will runn on the older 128M DRAM units 12.4(15)T11 I think, and 12.4(24)T1 on newer units. We have also played with DSL Modem firmware 3.0.33 and more recently 4.0.015 (which incidently works very well on UK ADSL2 Annex A). None have helped.
The connectivity in UK is PPPoA
It appears to be dependent on the amount of data through the DSL interface.
So a 24Mb/s connection will fail in hours, whereas a 9Mb/s will fail in days.
'sh int atm0' will show drops
'sh buffers' will show the middle and big buffers failing in particular.
Small packets such as ICMP and SSH will continue to work, so we can log on to the router(s) remotely.
But large packets such as those used for normal data will not pass the router reliably if at all.
Replace the router with a $100 item and the connection speed is normally better and there are no issues.
All these routers are similarly configured, have CBAC inspect code and a single IPSEC VPN.
MTU and MSS sizes are reduced to support IPSEC.
(though I hear the same problem from other UK deployments)
I have placed some info on the NetPro forum, seach for ADSL2+ and you should find it.
I have calls out to BT, large UK distributors and ISPs without any resolution or identification of the problem.
I think this is a significant issue given the value of Cisco DSL real estate in UK.