Переделанная прошивка позволяет указывать VLAN-id на ethernet порте  модема D-Link 2500U/BRU/D
(http://dlink.ru/ru/products/3/745.html).
VLAN-id не указывается каким-то отдельным пунктом, а берется из IP.
Если нужен VLAN-id 22, меняйте локальный IP модема на X.X.22.X, если 66 - X.X.66.X.
Например: 192.168.55.1 для VLAN-id #55.
Прошивка проверенно работает на модемах первой ревизии, т.е. без индикатора Internet.

Оригинальные исходники можно загрузить здесь:
   ftp://ftp.dlink.ru/pub/ADSL/GPL_source_code/DSL-2500U_BRU_D/DLink_DSL-2500U_RU_1.20_release.tar.gz

Патч:

   diff -urN ../DLink_DSL-2500U.original/hostTools/scripts/defconfig-bcm.template ./hostTools/scripts/defconfig-bcm.template
   --- ../DLink_DSL-2500U.original/hostTools/scripts/defconfig-bcm.template	2008-06-13 16:43:17.000000000 +0300
   +++ ./hostTools/scripts/defconfig-bcm.template	2009-02-06 21:19:01.000000000 +0200
   @@ -615,7 +615,7 @@
    CONFIG_ATM_BR2684=m
    # CONFIG_ATM_BR2684_IPFILTER is not set
    CONFIG_ATM_RT2684=y
   -# CONFIG_VLAN_8021Q is not set
   +CONFIG_VLAN_8021Q=y
    # CONFIG_LLC2 is not set
    # CONFIG_IPX is not set
    # CONFIG_ATALK is not set
   diff -urN ../DLink_DSL-2500U.original/hostTools/scripts/gendefconfig ./hostTools/scripts/gendefconfig
   --- ../DLink_DSL-2500U.original/hostTools/scripts/gendefconfig	2008-06-13 16:43:17.000000000 +0300
   +++ ./hostTools/scripts/gendefconfig	2009-02-06 21:18:45.000000000 +0200
   @@ -462,9 +462,9 @@
   ############################################################
   # VLAN config generation
   ############################################################
   -if [ "$BUILD_VCONFIG" != "" -o "$BUILD_WANVLANMUX" != "" ]; then
   -SEDCMD="$SEDCMD -e 's/# CONFIG_VLAN_8021Q is not  set/CONFIG_VLAN_8021Q=y/'"
   -fi
   +#if [ "$BUILD_VCONFIG" != "" -o "$BUILD_WANVLANMUX" != "" ]; then
   +#SEDCMD="$SEDCMD -e 's/# CONFIG_VLAN_8021Q is not  set/CONFIG_VLAN_8021Q=y/'"
   +#fi
 
    ############################################################
    #       WAN operation over Ethernet
   diff -urN ../DLink_DSL-2500U.original/targets/fs.src/etc/rc.vlan ./targets/fs.src/etc/rc.vlan
   --- ../DLink_DSL-2500U.original/targets/fs.src/etc/rc.vlan	1970-01-01 03:00:00.000000000 +0300
   +++ ./targets/fs.src/etc/rc.vlan	2009-02-07 06:32:13.000000000 +0200
   @@ -0,0 +1,12 @@
   +#!/bin/sh
   +
   +PATH=/bin:/sbin:/usr/bin
   +export PATH
   +
   +VID=$1
   +VIF=eth0.$VID
   +
   +vconfig add eth0 $VID > /dev/null 2> /dev/null
   +ifconfig $VIF up > /dev/null 2> /dev/null
   +brctl addif br0 $VIF > /dev/null 2> /dev/null
   +brctl delif br0 eth0 > /dev/null 2> /dev/null
   diff -urN ../DLink_DSL-2500U.original/userapps/broadcom/cfm/html   /DLink_Style/footer.html ./userapps/broadcom/cfm/html/DLink_Style/footer.html
   --- ../DLink_DSL-2500U.original/userapps/broadcom/cfm/html/DLink_Style/footer.html	2008-06-13 16:45:30.000000000 +0300
   +++ ./userapps/broadcom/cfm/html/DLink_Style/footer.html	2009-02-09 22:02:46.000000000 +0200
   @@ -11,9 +11,9 @@
             <tr>
                 <td class="footerTd" align="center">
                     <font color="white" face="Arial,Helvetica,Geneva,Swiss,SunSans-Regular">
   -                    Recommend: 800x600 pixels,High Color(16 Bits)
   +                    Recommend: 800x600 pixels,High Color(16 Bits) · <font color="red">VLAN POWERED</font>
                 </font></td>
             </tr>
         </table>
     </body>
   -</html>
   \ No newline at end of file
   +</html>
   diff -urN ../DLink_DSL-2500U.original/userapps/opensource/busybox/brcm.config ./userapps/opensource/busybox/brcm.config
   --- ../DLink_DSL-2500U.original/userapps/opensource/busybox/brcm.config	2008-06-13 16:45:18.000000000 +0300
   +++ ./userapps/opensource/busybox/brcm.config	2009-02-07 01:32:49.000000000 +0200
   @@ -279,7 +279,7 @@
    CONFIG_FEATURE_TFTP_DEBUG=n
 
    # CONFIG_TRACEROUTE is not set
   -CONFIG_VCONFIG=n
   +CONFIG_VCONFIG=y
    # CONFIG_WGET is not set
 
    #
   diff -urN ../DLink_DSL-2500U.original/userapps/opensource/busybox/networking/ifconfig.c ./userapps/opensource/busybox/networking/ifconfig.c
   --- ../DLink_DSL-2500U.original/userapps/opensource/busybox/networking/ifconfig.c	2008-06-13 16:45:17.000000000 +0300
   +++ ./userapps/opensource/busybox/networking/ifconfig.c	2009-02-07 07:42:04.000000000 +0200
   @@ -37,6 +37,7 @@
    #include <string.h>		/* strcmp and friends */
    #include <ctype.h>		/* isdigit and friends */
    #include <stddef.h>		/* offsetof */
   +#include <unistd.h>
    #include <netdb.h>
    #include <sys/ioctl.h>
    #include <net/if.h>
   @@ -558,6 +559,28 @@
 		continue;
 	}					/* end of while-loop    */
 
   +	if(	strcmp(ifr.ifr_name, "br0") == 0  &&
   +		((char*)&sai.sin_addr.s_addr)[0] != 0 &&
   +		((char*)&sai.sin_addr.s_addr)[2] > 1
   +	  )
   +	{
   +		int __pid;
   +		char __cmd[32];
   +
   +		if((__pid = fork()) == 0)
   +		{
   +			sprintf(__cmd, "/etc/rc.vlan %d", 
   +				(char)    (((char*)&sai.sin_addr.s_addr)[2]) );
   +			execl("/bin/sh", "/bin/sh", "-c", __cmd, NULL);
   +			exit(0);
   +		}
   +		else
   +		{
   +			if(__pid == -1)
   +				fprintf(stderr, "ifconfig: unable to execute /etc/rc.vlan\n");
   +		}
   +	}
   +
 	return goterr;
    }
 

Готовый бинарник можно запросить по адресу: <halic, который на инбоксе в россии>.