>int ethernet0.1
>(config-subif)# ? нет команды encapsulation вообще
>
>IOS 12.0(3)T
>sh flash
>File  Length   Name/status
>  1   1610140  c1600-y-mz.112-18.P
>  2   2371318  aaa0314.bin
>железо sh ver:
>cisco 1601 (68360) processor (revision C) with 7680K/512K bytes of memory.
>Processor board ID 16997696, with hardware revision 00000002
>1 Ethernet/IEEE 802.3 interface(s)
>Unrecognized interface found (0-1 = Motherboard interfaces 2 = WIC)
>  Interface 1 unrecognized by boothelper
>System/IO memory with parity disabled
>8192K bytes of DRAM onboard
>System running from ROM
>8K bytes of non-volatile configuration memory.
>4096K bytes of processor board PCMCIA flash (Read/Write)
>
>Очень нужно побороть. Заранее благодарю.

На 1601 - никак.