{"id":139001,"date":"2012-01-11T09:51:00","date_gmt":"2012-01-11T01:51:00","guid":{"rendered":"\/2012\/01\/11\/dual_nic.html"},"modified":"2012-01-11T09:51:00","modified_gmt":"2012-01-11T01:51:00","slug":"dual_nic","status":"publish","type":"post","link":"https:\/\/blog.zhenglei.net\/?p=139001","title":{"rendered":"Dual NIC configuration on Ubuntu"},"content":{"rendered":"

Suppose there are two NIC on one Ubuntu box:<\/p>\n

nic0:   eth0 
        ip=192.168.127.88
        gateway=192.168.127.2
        <\/p>\n

nic1:   eth1
        ip=172.24.220.72
        gateway=172.24.220.1<\/p>\n

 <\/p>\n

And the original networking configuration is:<\/p>\n

> netstat -arp<\/p>\n

172.24.0.0       *                    255.255.0.0     U          0 0            0 eth1
link-local           *                   255.255.0.0     U          0 0            0 eth0
192.168.0.0     *                    255.255.0.0     U          0 0            0 eth0
default         192.168.127.2   0.0.0.0            UG         0 0           0 eth0<\/p>\n

 <\/p>\n

In the above network configuration,   eth0 will be used as default gateway of server, all output traffic will go through eth0, except the target address is 172.24.0.0\/16.<\/p>\n

 <\/p>\n

issue:<\/p>\n

if one 172.24.0.0\/16  client access service via eth0, the return IP trafic will go through eth1, instead of erh0, according to the route table.<\/p>\n

 <\/p>\n

Solution:  Using policy route mechanism of linux:<\/p>\n

 <\/p>\n

Step 1 ******    Add extra route table for eth1 & eth0:<\/p>\n

    # echo “251   eth1” >>\/etc\/iproute2\/rt_tables<\/em><\/span><\/p>\n

    # echo “250   eth1” >>\/etc\/iproute2\/rt_tables<\/em><\/span><\/p>\n

 <\/p>\n

Step 2 ******   Setup eth1 route table:<\/p>\n

    #  ip route add 172.24.220.0\/24 dev eth1 src 172.24.220.72 table eth1
    #  ip route add default via 172.24.220.1 dev eth1 table eth1<\/em><\/span><\/p>\n

    # ip route add 192.168.127.0\/24 dev eth0 src 192.168.127.88 table eth0
    # ip route add default via 192.168.127.2 dev eth0 table eth0<\/em><\/span><\/p>\n

 <\/p>\n

Step 3 ******   Setup rule of eth0 & eth1 table:<\/p>\n

  # ip rule del prio 1000
  # ip rule del prio 2000<\/p>\n

  # ip rule add from 172.24.220.72\/16  table eth1 prio 1000
  # ip rule add from 192.168.127.88\/16 table eth0 prio 2000<\/em><\/span><\/p>\n

 <\/p>\n

Step 4 ******   Remove eth1 entry in the default  table:<\/p>\n

  # sudo route del -net 172.24.0.0\/16<\/em><\/span><\/p>\n

 <\/p>\n

Step 5 ******   Clean route table cache<\/p>\n

 # sudo ip -s -s route flush cache<\/em><\/span><\/p>\n

 <\/p>\n

Example:<\/p>\n

# cat  \/etc\/network\/interfaces<\/strong><\/p>\n

auto lo
iface lo inet loopback<\/p>\n

auto  eth0
iface eth0 inet dhcp<\/p>\n

auto eth1
iface eth1 inet dhcp
    post-up \/etc\/init.d\/seteth1mask.sh<\/em><\/p>\n

 <\/p>\n

#cat  \/etc\/init.d\/seteth1mask.sh<\/strong><\/p>\n

#! \/bin\/sh
\/sbin\/ifconfig eth1 netmask 255.255.0.0
\/sbin\/route add -host 172.24.61.252 gw 192.168.127.2 dev eth0<\/p>\n

ip route add 172.24.220.0\/24 dev eth1 src 172.24.220.72 table eth1
ip route add default via 172.24.220.1 dev eth1 table eth1<\/p>\n

ip route add 192.168.127.0\/24 dev eth0 src 192.168.127.88 table eth0
ip route add default via 192.168.127.2 dev eth0 table eth0<\/p>\n

ip rule del prio 1000
ip rule del prio 2000<\/p>\n

ip rule add from 172.24.220.72\/16 table eth1 prio 1000
ip rule add from 192.168.127.88\/16 table eth0 prio 2000<\/p>\n

ip route flush cache
\/sbin\/route del -net 172.24.0.0\/16<\/em><\/p>\n

 <\/p>\n

 <\/p>\n

****** Note ******<\/p>\n

  Before network link switch on windows xp\/samba client,  need to clean the network cache on windows system by logout action<\/p>\n


<\/em><\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

multi-homed Linux network configuration \u7ee7\u7eed\u9605\u8bfb →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,2],"tags":[82],"class_list":["post-139001","post","type-post","status-publish","format-standard","hentry","category-internet","category-linux","tag-route-linux"],"_links":{"self":[{"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/posts\/139001","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=139001"}],"version-history":[{"count":0,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=\/wp\/v2\/posts\/139001\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=139001"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=139001"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.zhenglei.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=139001"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}