CODEWITHSUNDEEP
linuxnetwork-programmingubuntuiproutes
Maxim Nikitenko
Maxim Nikitenko

Reputation: 31

ip route src not working

1I need to use several IPs on interface in Linux, and switch it, but it's not working.
for example:

# ifconfig
eth0      Link encap:Ethernet  HWaddr 90:2b:34:33:80:65  
          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::922b:34ff:fe33:8065/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:13220652 errors:0 dropped:32864 overruns:0 frame:0
          TX packets:8296620 errors:0 dropped:0 overruns:0 carrier:1
          collisions:0 txqueuelen:1000 
          RX bytes:16166162509 (16.1 GB)  TX bytes:2186645852 (2.1 GB)
          Interrupt:48 

eth0:1    Link encap:Ethernet  HWaddr 90:2b:34:33:80:65  
          inet addr:192.168.1.99  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              Interrupt:48 

lo        Link encap:Локальная петля (Loopback)  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:276685 errors:0 dropped:0 overruns:0 frame:0
          TX packets:276685 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:21387439 (21.3 MB)  TX bytes:21387439 (21.3 MB)

# ip route
169.254.0.0/16 dev eth0  scope link  metric 1000 
192.168.1.0/24 dev eth0  scope link  src 192.168.1.99 

# ping 192.168.1.50
PING 192.168.1.50 (192.168.1.50) 56(84) bytes of data.
64 bytes from 192.168.1.50: icmp_req=1 ttl=255 time=1.21 ms
64 bytes from 192.168.1.50: icmp_req=2 ttl=255 time=1.07 ms
64 bytes from 192.168.1.50: icmp_req=3 ttl=255 time=1.05 ms

and then i use Curl

# curl 192.168.1.50

and tcpdump:

13:24:02.009094 IP 192.168.1.1 > 192.168.1.50: ICMP echo request, id 8919, seq 347, length 64
E..T..@.@..%.......2...s"..[...P....q#...................... !"#$%&'()*+,-./01234567
13:24:02.010087 IP 192.168.1.50 > 192.168.1.1: ICMP echo reply, id 8919, seq 347, length 64
E..T...........2.......s"..[...P....q#...................... !"#$%&'()*+,-./01234567
13:43:40.006264 IP 192.168.1.1.48275 > 192.168.1.50.80: Flags [S], seq 3496592766, win 14600, options [mss 1460,sackOK,TS val 15698502 ecr 0,nop,wscale 7], length 0
E..<O8@[email protected].~......9............
...F........
13:43:40.007663 IP 192.168.1.50.80 > 192.168.1.1.48275: Flags [S.], seq 3006420619, ack 3496592767, win 5792, options [mss 1460,sackOK,TS val 151247914 ecr 15698502,nop,wscale 0], length 0
E..<..@[email protected].................
    ..*...F....

and source ip is still 192.168.1.1, what am i doing wrong?

UPD: BTW, just tryed same thing on Ubuntu 10.04 with 2.6.32 kernel, everything works good, and you even dont need to add "-I" to "ping" command, it seams in my kernel (3.2.0) somebody broken this feature.

Upvotes: 3

Views: 3911

Answers (2)

NRajK
NRajK

Reputation: 11

try adding a specific route like below:

ip route add 192.168.1.50/32 dev eth0 proto static src 192.168.1.99

this should result in any traffic to 192.168.1.50 being sent with a src-ip of 192.168.1.99...instead of default 192.168.1.1

Upvotes: 1

David Schwartz
David Schwartz

Reputation: 182763

The src option only affects packets whose source address is chosen by the operating system. The ping program chooses its own source address. If you want to influence its choice, use the -I or -B options. If you want to see if your src option is working, make a TCP connection or send a UDP datagram.

Upvotes: 2

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