Ssh client through a specific interface

Question

How can i force a client connection ssh to communicate through a specific interface ?

I have a server with eth0 and eth1 i.e., and i want to force all ssh clients to pass through eth0. So i could access my server via eth1 faster when there is a lot of ssh clients on my server.

Edit : It's the server who initiates the ssh client connections.

Answer 1

Update OPs edit asks for server side solution - this is client side. For temporary use you can bind option to SSH from particular IP or ethernet port. ssh target_IP -b source_IP

For more permanent solution change the routing table.

I cam trying to ssh into 172.x.x.69 from 172.x.x.7 (eth0) which has another Ethernet port 172.x.x.8 (eth1) that happens to be the default gateway.

Fails if i try to ssh directly - because this source IP defaults to x.x.x.8 eth1 and this is not allowed in external firewall rules to .69

# ssh 172.29.179.69 -l root
ssh: connect to host 172.x.x.69 port 22: Connection timed out
#

Success when I bind SSH to x.x.x.7 IP (eth0) using the -b switch - this IP is allowed to connect to .69 in firewall rules.

# ssh 172.x.x.69 -b 172.x.x.7 -l root
Last login: Wed Nov 19 14:27:44 2014 from 172.x.x.7
#

At 172.x.x.7 I have two ethernet ports x.7 and x.8

# ifconfig 
eth0      Link encap:Ethernet  HWaddr xxxxx
          inet addr:172.x.x.7  Bcast:172.x.x.31  Mask:255.255.255.224
          inet6 addr: xxx Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:27678 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1852058 (1.7 MiB)  TX bytes:684 (684.0 b)

eth1      Link encap:Ethernet  HWaddr xxx
          inet addr:172.x.x.8  Bcast:172.x.x.31  Mask:255.255.255.224
          inet6 addr: xxx Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:72022 errors:0 dropped:0 overruns:0 frame:0
          TX packets:34734 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:40788643 (38.8 MiB)  TX bytes:4441314 (4.2 MiB)

The reason I need this hack is the routing table default eth1 instead of eth0

# route (@172.x.x.7)
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
172.x.x.0       *               255.255.255.224 U     0      0        0 eth1
172.x.x.0       *               255.255.255.224 U     0      0        0 eth0
192.168.1.0     *               255.255.255.0   U     0      0        0 eth2
link-local      *               255.255.0.0     U     1002   0        0 eth0
link-local      *               255.255.0.0     U     1003   0        0 eth1
link-local      *               255.255.0.0     U     1004   0        0 eth2
default         172.x.x.1       0.0.0.0         UG    0      0        0 eth1 # eth0 OK
#