Router configuration question

[maniac]

Hello all, long time no see from me.

 

Now working in business, so this forum is less relevant to me now, however occasionally the odd issue crops up like the following.

 

I have a Sonicwall firewall in this business which is our perimeter device, and it has 5 ports on. I'm in the middle of some massive network changes here so all 5 are currently in use. I have 3 ADSL lines coming into it and at the moment 2 separate LAN segments because I'm re-addressing this network. We have also just had a fibre line connected and I am keen to move services across to this ASAP, but need to do so without interrupting the existing ADSL connections for now as they all handle various incoming/outgoing services which need to stay live while I do this.

 

So the question is how to free up a router port. Easy solution I thought, combine both the LAN segments onto one router port since they are on different VLAN's and the router can create virtual LAN ports, should be easy right?

 

So at the moment I have LAN segment 132.140.x.x (Don't ask about that IP address range, I inherited it) on port 0 and LAN segment 10.100.x.x on router port 4. They are both connected to their respective VLAN on my network which is a port on the switch with the untagged VLAN set appropriately. Great this all works. The Sonicwall router is also the default router for Lan Segment 132.140.x.x but for my new network the routing is all handled by the switch with a static IP route to send traffic out to the internet on the appropriate IP address. This has been working absolutely fine for the last 2 months or so.

 

Hope you're still with me!

 

So to move both LAN segments onto one router port I'm doing the following

 

Set VLAN 999 (which is my internet VLAN) as tagged on the router port that currently handles just the 132.140.x.x network

Remove the IP address from router port 4 which stops all internet traffic on the 10.100.x.x range as expected

Add a virtual LAN port on interface 0 with VLAN 999 specified and the same IP address as router port 4 had previously.

 

By my reckoning because the VLAN is set as tagged on both the router and the switch it should work, but it doesn't! I get no internet access on my 10.100.x.x network after making this change, but the 132.140.x.x network carries on as usual.

 

HOWEVER, this is the odd thing. From an SSH session on the core switch I can ping both the router on it's VLAN 999 address and ping outside of the network, but only from the switch not from any of the network segments. Looking at the ARP list it also shows the correct IP address is on the correct port, so the switch is communicating with the router on VLAN 999 on that port, it knows which port to send traffic to for that IP address, just for some bizarre reason I have no connectivity from any of my machines even thou it's actually the same VLAN and same address that it was communicating perfectly happily on just moments previously on the other router port.

 

Can anyone see what I'm potentially doing wrong because I'm stumped at the moment!

 

Cheers,

 

Mike.

Edited January 28, 2016 by maniac

[ReBoot]

I would take a look at the routing table on the Sonicwall (assume that's possible) to make sure you have all routes present and pointing to the correct subinterfaces/gateways. Do the same on the switch.

 

Also double check your VLAN setup and virtual LAN port.

[maniac]

Thanks, you were actually correct, but I managed to get there myself in the mean time. I realised it was EXACTLY the same problem I had when I first set it up, I needed a static route on the Sonicwall to send the traffic back to the network switch as by default the router assumes it is the default gateway, which it isn't for my network. As soon as I sorted that out it worked as expected. It's ALWAYS the simple things!

[ReBoot]

Good news glad you sorted things out !

[twin--turbo]

A common Gotcha.

 

 

TT