In case you see these missing icmp_seq numbers:

[root@mdskvm-p01 ~]# ping 192.168.0.149
PING 192.168.0.149 (192.168.0.149) 56(84) bytes of data.
64 bytes from 192.168.0.149: icmp_seq=1 ttl=64 time=0.536 ms
64 bytes from 192.168.0.149: icmp_seq=3 ttl=64 time=0.240 ms
64 bytes from 192.168.0.149: icmp_seq=7 ttl=64 time=0.330 ms
64 bytes from 192.168.0.149: icmp_seq=11 ttl=64 time=0.331 ms
64 bytes from 192.168.0.149: icmp_seq=15 ttl=64 time=0.353 ms
64 bytes from 192.168.0.149: icmp_seq=19 ttl=64 time=0.271 ms
 

Then you should check ifcfg-bond0 setting:

BONDING_OPTS='mode=4 miimon=100'

In our case, we had 2/4 NIC ports plugged into the switch so the above tried to do link aggregation using inactive ports.

BONDING_OPTS='mode=1 miimon=100'

We also tried mode=2 but that didn't work.  Further reading is available from RedHat Bonding Modes.

Some of the other common issues exibited by this include:

no route to host
Destination Host Unreachable

Cheers,
Tom