Теоретично - реально.
1. Обговорення на форумі dlink http://forum.dlink.ru/viewtopic.php?f=6&t=72355
2.
Ніби є можливість на нього поставити OpenWrt 10.03
(On EU and USA market router branded as 2640B, on Russian market - as 2640U (HW rev B2). This model fully supported in OpenWrt 10.03 (except of ADSL, since Broadcom didnt released source code of their drivers). ) http://wiki.openwrt.org/toh/d-link/dsl-2640u