iptables - 一个规则的两个条目| iptables -A INPUT -s localhost -j ACCEPT

Question

我从shell提示符发出以下规则：

iptables -A INPUT -s localhost -j ACCEPT

之后，当我检查iptables -L时，我看到两个相同的条目。

iptables-save -c摘要前后：

root@debian:~# iptables-save -c
# Generated by iptables-save v1.4.21 on Fri Nov  3 09:11:15 2017
*filter
:INPUT ACCEPT [8:528]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [5:492]
COMMIT
# Completed on Fri Nov  3 09:11:15 2017
root@debian:~# iptables -A INPUT -s localhost -j ACCEPT
root@debian:~# iptables-save -c
# Generated by iptables-save v1.4.21 on Fri Nov  3 09:11:24 2017
*filter
:INPUT ACCEPT [6:396]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [4:496]
[0:0] -A INPUT -s 127.0.0.1/32 -j ACCEPT
[0:0] -A INPUT -s 127.0.0.1/32 -j ACCEPT
COMMIT
# Completed on Fri Nov  3 09:11:24 2017
root@debian:~#

任何想法，为什么一条规则有两个条目？