My question is: How can I reliably set up a static route in OS X, for 2 endpoints to pass via a gateway, where all machines are on the same subnet? I provide the context below:
For testing purposes, I need to be able to set up a specific route between 2 endpoints on the same local subnet - an OS X (10.9) MacBook and a Linux-based 'receiver'.
The behaviour needs to be such that the next hop for traffic leaving the MacBook will be a FreeBSD-based QoS machine and not the standard default gateway. The BSD machine may also sit on the same subnet, and performs SNAT to masquerade new traffic and re-translates upon return.
Simplified, my environment is similar to the following:
Local subnet = 10.160.0.0/16
MacBook = 10.160.2.100
Linux Receiver = 10.160.2.200
Default Gateway for standard devices = 10.160.0.1
Example configuration of the BSD gateway:
en0 10.160.2.160
en1 10.160.3.170
netmask 255.255.0.0
gateway 10.160.0.1
An example of the desired flow:
REQUEST: MacBook --> BSD --> DefaultGateway --> Receiver
RESPONSE: Receiver --> DefaultGateway --> BSD --> MacBook
I see 3 problems occurring:
If I set the default gateway for en0 (the only active interface) onOS X to be the BSD machine on say 10.160.2.160, this works for awhile until this default route is automatically overwritten by OS Xto be the standard default of 10.160.0.1
I am also running into issues when configuring static routes in OS Xusing:
route add 10.160.2.200 10.160.2.160.. in this case one of 2 things happens - either the route works for a while displaying the netstat UGHS flags, and is then overwritten by OS X after which netstat includes the M flag to indicate that it was overwritten by a redirect..
..or the route does not work at all as there must be some other route taking precedence. Traceroute confirms this.
Netstat output after initial configuration:
jiosxserver:~ julianivory$ netstat -nrRouting tablesInternet:Destination Gateway Flags Refs Use Netif Expiredefault 10.160.2.160 UGSc 17 0 en010.140.1.31 10.160.2.160 UGHS 0 0 en010.140.1.35 10.160.1.1 UGHS 0 0 en010.160/16 link#4 UCS 5 0 en010.160.0.1 0:14:22:20:1c:d9 UHLWIir 14 0 en0 119110.160.1.37 0:50:56:8a:87:e9 UHLWIi 0 0 en0 113810.160.2.160 8e:af:b2:47:7f:91 UHLWIir 4 0 en0 114410.160.3.75 127.0.0.1 UHS 0 0 lo010.160.3.79 a8:20:66:27:72:2e UHLWIi 0 1 en0 118410.160.255.255 ff:ff:ff:ff:ff:ff UHLWbI 0 44 en0127 127.0.0.1 UCS 0 0 lo0127.0.0.1 127.0.0.1 UH 9 20602 lo0169.254 link#4 UCS 0 0 en0...and Traceroute output shows that the default route is not in use:
traceroute to 8.8.8.8 (8.8.8.8), 64 hops max, 52 byte packets 1 10.160.0.1 (10.160.0.1) 0.504 ms 0.237 ms 0.217 ms 2 192.168.2.1 (192.168.2.1) 1.065 ms 1.020 ms 0.973 ms 3 name-removed (xx.1xx.xxx.1) 14.250 ms 13.688 ms 14.046 ms 4 xxx.xxx.178.141 (xxx.xxx.178.141) 14.196 ms 14.121 ms 13.967 ms
...after some time, the default gateway will have 'automagically' been changed to 10.160.0.1...
Any thoughts or suggestions would be appreciated hugely.
