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Vlans and switch route to Internet

Posted on 2011-03-15
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Last Modified: 2012-05-11
I'm not sure if this is a problem or a misconfiguration but I could do with some help please.

We have a HP A5120 SI 3 layer switch setup with 2 Vlans,  Vlan 1 172.18.4.2/23 and Vlan 2  172.18.20.2/22 the switch trunks to a Sonicwall TZ210 for internet access.  

The Sonicwall has two subinterfaces 172.18.4.1/23 and 172.18.20.1/22 for both subnets, I can ping the switch interfaces and Sonicwall subinterfaces from the Vlans.  

The problem I'm having is with the default route for internet access. What should this be??

If I add the following 2 routes only one route shows as active and that specific Vlan has Internet access, if I remove one off the static routes then the remaining route becomes active.

What I need is both routes to be active so both Vlans can access the internet at the same time.

Static routes
0.0.0.0 0.0.0.0 172.18.4.1
0.0.0.0 0.0.0.0 172.18.20.1

I tried adding the Sonicwalls primary interface 192.168.100.1 as the default static route but the switch couldn't see the network, I assume the Sonicwall dropped the packets as per design.  

Any help/advise would be grateful as to how i can get both Vlans to share an internet connection.
Thanks
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Question by:HatchIT
9 Comments
 
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Expert Comment

by:fcontrepois
ID: 35139592
try the following

remove ip config on the router

on the switch create a new interface with ip 192.168.1.2/24
on the router create an interface with ip 192.168.1.1/24

on clients put the L3 switch as the default gateway
on the L3 switch put the 192.168.1.1 as the default gateway

bye
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Expert Comment

by:jimmyray7
ID: 35139757
If I recall the TZ series don't support VLAN tagging, so you'll either have to do what fcontrepois said or put the uplinks on different switch ports and plug them into two interfaces on the sonicwall (i.e. LAN 1 goes from port 1 on switch to X0 on TZ210, LAN 2 goes from port 2 to X2 on TZ210).

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Author Comment

by:HatchIT
ID: 35139854
The latest SonicOS 5.8 now supports Vlan tagging on the TZ210 so both Sonicwall subinterfaces are tagged accordingly X0:20 and X0:50

Thanks
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Expert Comment

by:RKinsp
ID: 35140028
You do not need static routes on the switch for this if the VLANs extend to the Sonicwall. What you need is to set the default gateway on your computers for the Sonicwall's IP's.

You might as well disable IP Routing on the switch, i really don't see the need to add another VLAN to it (192...).

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Author Comment

by:HatchIT
ID: 35140272
We looked at that option but we wanted the switch to do the routing between vlans so if anything happend to the Sonicwall the clients could still communicate across the vlans. We want the the Sonicwall to do just internet and vpn access going forward.
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Accepted Solution

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RKinsp earned 500 total points
ID: 35140375
Even if you have IP Routing enabled on the switch, it doesn't matter because of your default gateway. If you set the default gateway on your computers to 172.18.x.1, the packet will go go the Sonicwall because the VLAN is extended all the way there.

If you want to route locally, you have to remove the 172.18.x.x networks from the Sonicwall like fcontrepois said on the first post and create the 192.168.1.x network on the switch.

Important concept to remember is that a packet will only hit a Router Interface if it does not have the destination IP on the same VLAN, so by extending the Layer 2 all the way to the Sonicwall, your pretty much eliminating the need for Layer 3 on the switch.

-RK




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Assisted Solution

by:HatchIT
HatchIT earned 0 total points
ID: 35140616
RK, I think you hit the nail on the head, it all makes sense, Thanks.
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Expert Comment

by:RKinsp
ID: 35140733
Thanks Hatchit !

I think you might want to consider giving credit to fcontrepois as well. He didn't go into detail, but I think he meant the same thing on his first post.

Sincerely,
RK
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Author Closing Comment

by:HatchIT
ID: 35174558
RK, I think you hit the nail on the head, it all makes sense, Thanks
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