Linux rp_filter和arp_filter参数浅析

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已于 2022-04-22 16:57:23 修改

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分类专栏： Linux 文章标签： linux 运维 centos

于 2022-04-21 21:11:54 首次发布

本文链接：https://blog.youkuaiyun.com/qq_41586875/article/details/124331851

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本文详细介绍了Linux系统在默认配置下如何处理ARP请求，并通过修改`arp_ignore`参数来调整接口响应行为。实验中展示了不同`arp_filter`和`rp_filter`设置对ARP响应的影响，以及网络接口优先级变化后对外提供的MAC地址。此外，还通过`tcpdump`展示了在关闭过滤参数后，两张网卡同时对外响应的情况。

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在默认配置下，只要ARP请求中的目标IP配置在本机，无论其是否配置在收到ARP请求数据包的接口上，Linux收包接口都会以身MAC地址发送ARP响应。若是不希望接口响应所有本机IP，可以通过修改arp_ignore参数来调整

测试环境

网卡	IP
机器1-ens33	192.168.1.11
机器1-ens36	192.168.1.12
机器2-ens160	192.168.1.15
vmare1	192.168.1.1

实验

# 查看网络信息
[root@node1 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:ec:1c:2d brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.11/24 brd 192.168.1.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::624c:c1db:e3b4:9165/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: ens36: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:ec:1c:37 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.12/24 brd 192.168.1.255 scope global noprefixroute ens36
       valid_lft forever preferred_lft forever
    inet6 fe80::5dab:f84:95b8:1f/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever


# 查看此时路由信息
[root@node1 ~]# ip route
192.168.1.0/24 dev ens33 proto kernel scope link src 192.168.1.11 metric 100 
192.168.1.0/24 dev ens36 proto kernel scope link src 192.168.1.12 metric 101

# arp_filter和rp_filter全开
    sysctl -w net.ipv4.conf.all.arp_filter=1
    sysctl -w net.ipv4.conf.all.rp_filter=1
    sysctl -w net.ipv4.conf.ens36.arp_filter=1
    sysctl -w net.ipv4.conf.ens36.rp_filter=1
    sysctl -w net.ipv4.conf.default.arp_filter=1
    sysctl -w net.ipv4.conf.default.rp_filter=1
    sysctl -w net.ipv4.conf.ens33.arp_filter=1
    sysctl -w net.ipv4.conf.ens33.rp_filter=1
    sysctl -w net.ipv4.conf.lo.arp_filter=1
    sysctl -w net.ipv4.conf.lo.rp_filter=1


# 机器2 ping 192.168.1.12
[root@localhost ~]# ping 192.168.1.12
PING 192.168.1.12 (192.168.1.12) 56(84) bytes of data.
64 bytes from 192.168.1.12: icmp_seq=1 ttl=64 time=0.397 ms
64 bytes from 192.168.1.12: icmp_seq=2 ttl=64 time=0.393 ms
64 bytes from 192.168.1.12: icmp_seq=3 ttl=64 time=1.15 ms
64 bytes from 192.168.1.12: icmp_seq=4 ttl=64 time=0.583 

# 机器2查看arp,可以发现机器一对外只回复了ens33的MAC地址（因为ens36收到后，查询路由表发现需要把包从ens33发出，收发不是同一个接口，立刻把数据包丢了）
[root@localhost ~]# arp -n
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.1.12             ether   00:0c:29:ec:1c:2d   C                     ens160
192.168.1.1              ether   00:50:56:c0:00:01   C                     ens160
192.168.1.11             ether   00:0c:29:ec:1c:2d   C                     ens160

# 机器1升级ens36优先级
[root@node1 ~]# ip route
192.168.1.0/24 dev ens36 scope link 
192.168.1.0/24 dev ens33 scope link metric 100


# 机器2 查看MAC，发现此时对外MAC地址为ens36的了
[root@localhost ~]# arp -n
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.1.12             ether   00:0c:29:ec:1c:37   C                     ens160
192.168.1.1              ether   00:50:56:c0:00:01   C                     ens160
192.168.1.11             ether   00:0c:29:ec:1c:37   C                     ens160

# arp_filter和rp_filter全关
    sysctl -w net.ipv4.conf.all.arp_filter=0
    sysctl -w net.ipv4.conf.all.rp_filter=0
    sysctl -w net.ipv4.conf.ens36.arp_filter=0
    sysctl -w net.ipv4.conf.ens36.rp_filter=0
    sysctl -w net.ipv4.conf.default.arp_filter=0
    sysctl -w net.ipv4.conf.default.rp_filter=0
    sysctl -w net.ipv4.conf.ens33.arp_filter=0
    sysctl -w net.ipv4.conf.ens33.rp_filter=0
    sysctl -w net.ipv4.conf.lo.arp_filter=0
    sysctl -w net.ipv4.conf.lo.rp_filter=0

# 查看机器1 路由
[root@node1 ~]# ip route
192.168.1.0/24 dev ens33 proto kernel scope link src 192.168.1.11 metric 100 
192.168.1.0/24 dev ens36 proto kernel scope link src 192.168.1.12 metric 101

# 机器2 ping 机器1
[root@localhost ~]# ping -c 1 192.168.1.11
PING 192.168.1.11 (192.168.1.11) 56(84) bytes of data.
64 bytes from 192.168.1.11: icmp_seq=1 ttl=64 time=0.849 ms

--- 192.168.1.11 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.849/0.849/0.849/0.000 ms
[root@localhost ~]# ping -c 1 192.168.1.12
PING 192.168.1.12 (192.168.1.12) 56(84) bytes of data.
64 bytes from 192.168.1.12: icmp_seq=1 ttl=64 time=0.572 ms

--- 192.168.1.12 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.572/0.572/0.572/0.000 ms


# 查看机器的tcpdump抓包，发现现在二张网卡开始同时对外提供MAC地址了，在之前二张网卡只会对外响应一个MAC地址(但是在这种情况下先发的响应包可能会被后响应的覆盖)
[root@node1 ~]# tcpdump -i any arp -Nnv
tcpdump: listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
09:06:09.155324 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.11 tell 192.168.1.15, length 46
09:06:09.155351 ARP, Ethernet (len 6), IPv4 (len 4), Reply 192.168.1.11 is-at 00:0c:29:ec:1c:2d, length 28
09:06:09.155632 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.11 tell 192.168.1.15, length 46
09:06:09.155641 ARP, Ethernet (len 6), IPv4 (len 4), Reply 192.168.1.11 is-at 00:0c:29:ec:1c:37, length 28
09:06:10.834215 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.12 tell 192.168.1.15, length 46
09:06:10.834238 ARP, Ethernet (len 6), IPv4 (len 4), Reply 192.168.1.12 is-at 00:0c:29:ec:1c:2d, length 28
09:06:10.834330 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.12 tell 192.168.1.15, length 46
09:06:10.834336 ARP, Ethernet (len 6), IPv4 (len 4), Reply 192.168.1.12 is-at 00:0c:29:ec:1c:37, length 28