Output of cat /proc/ioports is:

[HTML]-bash-2.05b# cat /proc/ioports
0000-001f : dma1
0020-0021 : pic1
0022-0022 : PM2_CNT_BLK
0040-0043 : timer0
0050-0053 : timer1
0060-006f : keyboard
0070-0077 : rtc
0080-008f : dma page reg
00a0-00a1 : pic2
00c0-00df : dma2
00f0-00ff : fpu
0170-0177 : ide1
0376-0376 : ide1
03c0-03df : vga+
03f8-03ff : serial
0400-0403 : PM1a_EVT_BLK
0404-0405 : PM1a_CNT_BLK
0408-040b : PM_TMR
0410-0415 : ACPI CPU throttle
0420-0423 : GPE0_BLK
0450-0453 : GPE1_BLK
0500-050f : pnp 00:01
c000-cfff : PCI Bus #03
cc00-ccff : 0000:03:06.0
cc00-ccff : via-rhine
d000-dfff : PCI Bus #02
e000-efff : PCI Bus #01
ec00-ec7f : vt1211-isa
f000-f01f : 0000:00:10.2
f400-f41f : 0000:00:10.1
f800-f81f : 0000:00:10.0
fc00-fc0f : 0000:00:0f.0
[/HTML]

I expect that I could examine content of I/O port memory by doing:
dd if=/dev/port | hexdump -C | less

But I can't see all port addresses listed by previous command. In particular ec00-cc7f region.
[HTML]
0000cc60 00 00 00 00 00 00 00 00 00 00 00 00 01 04 06 00 |................|
0000cc70 80 41 6d 78 80 00 00 29 10 10 00 b0 00 00 00 00 |.Amx...)........|
0000cc80 00 00 1f 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
0000cc90 00 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00 |................|
0000cca0 00 00 04 00 00 00 04 00 00 00 00 00 00 00 00 00 |................|
0000ccb0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
0000ccc0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
0000cd00 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
*
0000f000 00 00 20 00 00 00 00 00 00 00 00 00 40 00 00 00 |.. .........@...|
0000f010 8a 04 8a 04 00 00 00 00 00 00 00 00 00 00 00 00 |................|
0000f020 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
*
0000f400 00 00 20 00 00 00 00 00 00 00 00 00 40 00 00 00 |.. .........@...|
0000f410 8a 04 8a 04 00 00 00 00 00 00 00 00 00 00 00 00 |................|
0000f420 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
*
0000f800 00 00 20 00 00 00 00 00 00 00 00 00 40 00 00 00 |.. .........@...|
0000f810 8a 04 8a 04 00 00 00 00 00 00 00 00 00 00 00 00 |................|
0000f820 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
*
0000fc00 00 00 00 00 00 00 00 00 00 00 04 00 00 00 00 00 |................|
0000fc10 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
*
00[/HTML]

Is there any way to examine content of IO Port space from command prompt?

The * on some lines indicates that all missing lines (other than the address) are the same as the one above. In your case, the missing address space is all 1bits (ff bytes).