Network Interfaces Problem - Monitoring equipment

Dear gurus of Linux / Unix.
I have a server, which I use to monitoring traffic, the problem that I find is when I run the following command:

probe:~ # sar -n DEV 1

I see that I one second appear info in some interface and in the other second no appear, I don't know what will be the problem?

probe:~ # sar -n DEV 1
Linux 2.6.32.12-0.7-default (lav1)     01/16/2013     _x86_64_

03:13:14 AM     IFACE   rxpck/s   txpck/s    rxkB/s    txkB/s   rxcmp/s   txcmp/s  rxmcst/s
03:13:15 AM        lo    237.11    237.11    133.59    133.59      0.00      0.00      0.00
03:13:15 AM      eth4      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM      eth7  85488.66      0.00  54044.70      0.00      0.00      0.00      0.00
03:13:15 AM      eth5      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM      eth6      1.03      0.00      0.08      0.00      0.00      0.00      1.03
03:13:15 AM      eth0      2.06      0.00      0.13      0.00      0.00      0.00      0.00
03:13:15 AM      eth1      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM      eth2      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM      eth3      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth0.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth0.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth1.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth1.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth2.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth2.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth3.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth3.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth4.2517  21923.71      0.00   3820.11      0.00      0.00      0.00      1.03
03:13:15 AM eth4.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth5.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth5.2518   3235.05      0.00    526.90      0.00      0.00      0.00      0.00
03:13:15 AM eth6.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:15 AM eth6.2518      1.03      0.00      0.07      0.00      0.00      0.00      1.03
03:13:15 AM eth7.2517  42420.62      0.00  26596.42      0.00      0.00      0.00      0.00
03:13:15 AM eth7.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00

03:13:15 AM     IFACE   rxpck/s   txpck/s    rxkB/s    txkB/s   rxcmp/s   txcmp/s  rxmcst/s
03:13:16 AM        lo    129.41    129.41     70.50     70.50      0.00      0.00      0.00
03:13:16 AM      eth4  40502.94      0.00   7743.55      0.00      0.00      0.00      0.98
03:13:16 AM      eth7      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM      eth5   6229.41      0.00   1096.53      0.00      0.00      0.00      0.00
03:13:16 AM      eth6      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM      eth0      1.96      1.96      0.13      2.49      0.00      0.00      0.00
03:13:16 AM      eth1      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM      eth2      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM      eth3      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth0.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth0.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth1.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth1.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth2.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth2.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth3.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth3.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth4.2517  19767.65      0.00   3568.61      0.00      0.00      0.00      0.00
03:13:16 AM eth4.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth5.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth5.2518   3170.59      0.00    526.46      0.00      0.00      0.00      0.00
03:13:16 AM eth6.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth6.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:16 AM eth7.2517  39611.76      0.00  24385.15      0.00      0.00      0.00      0.00
03:13:16 AM eth7.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00

03:13:16 AM     IFACE   rxpck/s   txpck/s    rxkB/s    txkB/s   rxcmp/s   txcmp/s  rxmcst/s
03:13:17 AM        lo      6.00      6.00      0.82      0.82      0.00      0.00      0.00
03:13:17 AM      eth4      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM      eth7  81707.00      0.00  51731.79      0.00      0.00      0.00      0.00
03:13:17 AM      eth5      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM      eth6      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM      eth0      2.00      2.00      0.13      2.54      0.00      0.00      0.00
03:13:17 AM      eth1      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM      eth2      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM      eth3      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth0.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth0.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth1.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth1.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth2.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth2.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth3.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth3.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth4.2517  20838.00      0.00   3690.83      0.00      0.00      0.00      0.00
03:13:17 AM eth4.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth5.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth5.2518   3331.00      0.00    549.41      0.00      0.00      0.00      0.00
03:13:17 AM eth6.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth6.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:17 AM eth7.2517  43083.00      0.00  27102.19      0.00      0.00      0.00      0.00
03:13:17 AM eth7.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00

03:13:17 AM     IFACE   rxpck/s   txpck/s    rxkB/s    txkB/s   rxcmp/s   txcmp/s  rxmcst/s
03:13:18 AM        lo     12.63     12.63      1.97      1.97      0.00      0.00      0.00
03:13:18 AM      eth4  43789.47      0.00   8420.30      0.00      0.00      0.00      0.00
03:13:18 AM      eth7      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM      eth5   6922.11      0.00   1251.02      0.00      0.00      0.00      0.00
03:13:18 AM      eth6      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM      eth0     11.58     13.68      0.77     18.97      0.00      0.00      0.00
03:13:18 AM      eth1      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM      eth2      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM      eth3      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth0.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth0.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth1.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth1.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth2.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth2.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth3.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth3.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth4.2517  21937.89      0.00   3962.40      0.00      0.00      0.00      0.00
03:13:18 AM eth4.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth5.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth5.2518   3447.37      0.00    590.10      0.00      0.00      0.00      0.00
03:13:18 AM eth6.2517      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth6.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
03:13:18 AM eth7.2517  45248.42      0.00  28402.57      0.00      0.00      0.00      1.05
03:13:18 AM eth7.2518      0.00      0.00      0.00      0.00      0.00      0.00      0.00
^C
probe:~ #

As you can see the problem appear in the interface eth4, eth5 and eth7, in one second appear info and the other not

A Guru that can help please to identify what will be the problem?

I hope your suggestion/comments

Best Regards
Andres