[ADSL] British Telecom, Cisco routers and ADSL2+


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Ran into an interesting problem with our current migration from 20C to 21C using Cisco 877 routers. The fault was simply that the ADSL connectivity was horrible with extremely frequent disconnects and reconnects.

Cisco ADSL routers ship with an embedded DSL firmware in the IOS. This firmware does not play nicely with BT equipment especially when running over ADSL2+. The solution? Upgrade the DSL firmware to 4.0.18 which has carrier specific (namely BT) enhancements to it.

Once you have the firmware you simply upload it to the flash: of the Cisco router and ensure (if running on an 877 model) it is called adsl_alc_20190.bin. (ADSL firmware for an Alcatel 20190 chipset)

    9  -rwx     1000952  Oct 19 2010 09:39:47 +00:00  adsl_alc_20190.bin
The file will override the embedded firmware in the current IOS on the router. To verify enter the following:

show dsl interface
Example output (from my router)
Init FW:         init_AMR_4.0.018.bin
Operation FW:    AMR-E-4.0.018.bin
FW Source:       external
FW Version:      4.0.18
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