Follow below link to send your log messages to remote server using tcp or udp ports
Generally all the info to error level messages are logged inside /var/log/messages but it makes hard to differentiate between long list of logs inside messages.
To separate the iptables related logs in different file follow the following procedure
NOTE: For RHEL 6 file name will be rsyslog.conf
To log all the iptables related messages
# vi /etc/syslog.conf
# Log all kernel messages to firewall.log.
kern.* /var/log/frewall.log
# Log anything (except mail) of level info or higher.
# Don't log private authentication messages!
# Don't log kernel related any messages
*.info;mail.none;authpriv.none;cron.none;kern.none /var/log/messages
To log only warning level iptables messages
# Log all kernel messages to firewall.log.
kern.warn /var/log/frewall-warn.log
To log all the messages for info level to error level
kern.info;kern.!crit /var/log/firewall.log
To log the messages as per their severity level in different files
kern.* /var/log/iptables.log
kern.crit /var/log/iptables-crit.log
kern.info /var/log/iptables-info.log
For more information on severity levels of syslog follow the below link
SYSLOG Tutorial
Once done restart the syslog services
For RHEL 6
# service rsyslog restart
For RHEL 5 or older
# service syslog restart
For example
Q. Create a rule to monitor the ping logs from 192.168.1.10 to the localhost
# iptables -I INPUT -s 192.168.1.10 -p icmp -j LOG --log-prefix "PING TEST "
Now let us verify it in our log file
Try to ping from 192.168.1.10 and observe the log file
# cat /var/log/iptables.log
Mar 6 11:22:36 test1 kernel: PING TEST IN=eth3 OUT= MAC=00:0c:29:51:aa:e1:00:0c:29:a3:f5:fa:08:00 SRC=192.168.1.10 DST=192.168.1.6 LEN=84 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=ICMP TYPE=8 CODE=0 ID=1037 SEQ=2
Mar 6 11:23:03 test1 kernel: PING TEST IN=eth3 OUT= MAC=00:0c:29:51:aa:e1:00:0c:29:a3:f5:fa:08:00 SRC=192.168.1.10 DST=192.168.1.6 LEN=84 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=ICMP TYPE=8 CODE=0 ID=3341 SEQ=1
Mar 6 11:23:04 test1 kernel: PING TEST IN=eth3 OUT= MAC=00:0c:29:51:aa:e1:00:0c:29:a3:f5:fa:08:00 SRC=192.168.1.10 DST=192.168.1.6 LEN=84 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=ICMP TYPE=8 CODE=0 ID=3341 SEQ=2
Learn how to use iptables in simple steps with examples using below links
Basic iptables tutorial I
Basic iptables tutorial II