На Linux это можно сделать командой ifconfig и netstat. На FreeBSD - командой netstat. Под Windows netstat -e (к сожалению, без указания конкретного интерфейса). Под IOS Cisco show interfaces имя_интерфейса. Примеры:  

Windows
D:\Documents and Settings\user>netstat -e
Interface Statistics
                           Received            Sent
Bytes                    1318170969      1331072579
Unicast packets            17579014        19350523
Non-unicast packets            7408            7298
Discards                          0               0
Errors                            0               0
Unknown protocols                 0 

Red Hat Linux
[root@localhost ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:C0:DF:0B:1D:08
          inet addr:a.b.11.111  Bcast:10.255.255.255  Mask:255.0.0.0
          inet6 addr: fe80::2c0:dfff:fe0b:1d08/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:12440467 errors:0 dropped:0 overruns:0 frame:0
          TX packets:54452 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1136982908 (1.0 GiB)  TX bytes:5774730 (5.5 MiB)
          Interrupt:169 Base address:0x1000
lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:1635 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1635 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1743404 (1.6 MiB)  TX bytes:1743404 (1.6 MiB)
[root@localhost ~]# netstat -i
Kernel Interface table
Iface       MTU Met    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0       1500   0 12564444      0      0      0    54645      0      0      0 BMRU
lo        16436   0     1635      0      0      0     1635      0      0      0 LRU

FreeBSD
fbsdhost# netstat -id
Name    Mtu Network       Address              Ipkts Ierrs    Opkts Oerrs  Coll Drop
fxp0   1500 <Link#1>      00:90:27:29:5b:8e 13622999     0 13319711     0     0    0
fxp0   1500 x.y.123/24    x.y.123.75          808197     -   492436     -     -    -
fxp1   1500 <Link#2>      00:d0:b7:28:60:71 12829912     0 12672411     0     0    0
fxp1   1500 a.b.7         a.b.7.254            33157     -    28485     -     -    -
plip0  1500 <Link#3>                               0     0        0     0     0    0
lo0   16384 <Link#4>                            1177     0     1177     0     0    0
lo0   16384 fe80:4::1     fe80:4::1                0     -        0     -     -    -
lo0   16384 localhost     ::1                      0     -        0     -     -    -
lo0   16384 your-net      localhost             1163     -     1163     -     -    -
fbsdhost# netstat -I fxp0 -d
Name    Mtu Network       Address              Ipkts Ierrs    Opkts Oerrs  Coll Drop
fxp0   1500 <Link#1>      00:90:27:29:5b:8e 13623198     0 13319942     0     0    0
fxp0   1500 x.y.123/24    x.y.123.75          808236     -   492463     -     -    -