4.7. Wrong location

It could also be that the Steelhead appliance is connected to a wrong device in the network. One possibility is described in the previous section, where the IP subnet configured on the in-path interface is wrong, possibly because the LAN/WAN interfaces are connected to the wrong switch.

But there is another possibility, where the Steelhead appliance is properly put between the WAN router and LAN switch, but there is also a normal cable directly connected between the WAN router and LAN switch.

Figure 4.15. Steelhead appliance by-passed with a cable.

Steelhead appliance by-passed with a cable.

There are four possibilities:

4.7.1. What can cause this?

This scenario can be caused in two ways:

  • The Steelhead appliance got installed and the technician didn't take out the cable.

  • The Steelhead appliance got installed, everything was fine and due to some reason later a site-technician sees that there is no cable between the LAN switch and WAN router and he thinks that this is a bad idea because he is only aware of scenarios without WAN optimizers and puts it back in.

These issues can be present but only manifest when the Steelhead appliance, WAN router, or LAN switch gets reset, and the devices need to re-discover the path to the MAC addresses of the default gateway, and that path bypasses the Steelhead appliance.

4.7.2. How to determine

4.7.2.1. With tcpdump

On a remote machine, start to ping a device behind the LAN switch. On the Steelhead appliance, run the tcpdump commands:

Figure 4.16. Run these tcpdump commands

SH # tcpdump -ni lan0 'icmp or (vlan and icmp)'
SH # tcpdump -ni wan0 'icmp or (vlan and icmp)'

If the traffic is going via the normal cable, you should only see the ICMP Echo Reply packets, the ICMP Echo Request packets or nothing at all.

4.7.2.2. On the LAN switch

To do this, you first need the MAC addresses of the LAN and WAN interfaces on the Steelhead appliance and the MAC address of the default gateway on the WAN router.

On the LAN switch, issue the command to see the ARP table. Search for the MAC address of the default gateway in the list and note down the outgoing port. Then search for the MAC addresses of the LAN and WAN interfaces in the list and note down the outgoing ports. These outgoing ports should be the same if the traffic goes via the Steelhead appliance.

4.7.2.3. On the WAN router

To do this, you first need the MAC addresses of the LAN and WAN interfaces on the Steelhead appliance and the MAC address of a device behind the LAN switch.

On the WAN router, issue the command to see the ARP table. Search for the MAC address of the LAN device in the list and note down the outgoing port. Then search for the MAC addresses of the LAN and WAN interfaces in the list and note down the outgoing ports. These outgoing ports should be the same if the traffic goes via the Steelhead appliance.