Hello All,
I've been trawling through the forums here and while I've found a lot of good advice, I haven't found anything that makes sense in my case. Here's what I have:
Two of our sites are being set up with a PLC network. The vendor has decided that the only good way to accomplish cross-site monitoring is to have both sites on the same subnet. I've asked them if they would please set them to separate subnets, but they refuse claiming that this shouldn't be an issue because they've done it this way at other client sites. That said, I understand it's not really the right way to do things but they won't listen to reason.
So, both sites are residing on the same subnet of 172.X.X.Z. We do have a bit of an advantage in this situation and that is the way our sites are connected. Our switches are connected directly to each other using a telco provided ethernet connection. No MPLS, no VPN, just a direct connection. The telco equipment is completely transparent to the switches.
The switchports that are connected on each end are set up like so:
interface GigabitEthernet1/0/14
description xxxxxxx
switchport access vlan 5 (This shouldn't matter since it's been set to trunk mode)
switchport trunk encapsulation dot1q
switchport trunk native vlan 5
switchport trunk allowed vlan 5,172
switchport mode dynamic desirable
Now, if I set up a vlan interface with the 172.X.X.1 IP address on either side of the link the respective server is able to see the interface. So, the VLAN is working from the servers to the switches on both sides. However, the actual communication between the two servers (and all the PLCs on either side of the network) isn't working. It seems pretty obvious that the problem is happening somewhere on the link between the two switches but for the life of me I cannot figure out where.
Another small gotcha is that the servers are both set to use 172.X.X.1 as their default gateway. I had thought at one point that if I set up a VLAN Interface on both sides, one with .1 and one with .2 and set the servers to use those as their respective gateways that this might solve the problem. However, I'm not entirely sure if that will work if it will, whether it will require anything special or if it would be sufficient to just go
Conf t
interface vlan 172
ip address 172.X.X.1 255.255.255.0
(And similar for .2)
Thanks in advance for any help you can offer!
-Josh
