Connectivity Issue with RV042G and SG300-10 Switch (Layer 3)

[Romeo Sulzer]

Due to its dual WAN feature, we replaced our Linksys EA4500 Router with a Cisco RV042G. Attached to the RV042G router is a Cisco SG300-10 Switch in Layer 3 Mode. The LAN is structured as follows:

VLAN 100 (Internal Clients)

• 10.1.1.0 / 24
• Default Gateway: 10.1.1.1 (RV042G)
• SG300 Interface:  10.1.1.254
• DHCP Relay to 10.1.0.200
• DNS for Clients: 10.1.0.200

VLAN200 (Guest Clients)

• 10.1.2.0 / 24
• Default Gateway: 10.1.2.254 (SG300 IPV4 Interface)
• DHCP Relay to 10.1.0.200
• DNS for Clients: 10.1.0.200

VLAN 300 (Servers)

• 10.1.0.0/ 24
• Default Gateway: 10.1.0.254 (SG300 IPV4 Interface)
• DNS and DHCP Server: 10.1.0.200

On the RV042G I’ve added the following static routes:

• 10.1.0.0 / 24
• Next hop: 10.1.1.254
• Metric: 1

• 10.1.2.0 / 24
• Next hop: 10.1.1.254
• Metric: 1

On the Linksys EA4500 this configuration worked without any issues. However, with the RV042G I cannot access the internet when I connect to VLAN  on the SG300. If I connect directly to one of the LAN ports of the RV042, I can access the internet without any issues.  It looks like a routing issue, since a tracert revealed a time out after reaching the SG300’s IPV4 Interface (10.1.0.254 and 10.1.2.254). I’ve verified that there is a static route to 10.1.1.0 / 24 on the SG300.

Any obvious things I’ve missed?

Thank you for your appreciated help!

[Romeo Sulzer]

I was able to solve the issue described above by adding the VLAN subnets under Setup -> Network -> IPv4 -> Multiple Subnets.

I've noticed that in the RV042G you can only add up to 5 additional subnets, our network has more than that.  Is there any work around?  Could this limitation be removed/increased in a future firmware update?

[chrebert]

Hello Romeo,

You are correct in the work around you came up with.

The RV042 does not NAT for non-native VLANs (as in VLANs that it does not known about) so unless you create those VLANs on the RV042, those subnets from your layer 3 switch won't be able to get out to the internet.

From what I've seen there are no plans to increase this number, since the RV042 can only support a few VLANs to begin with.

You can however go with an RV220W or ISA as they do have the ability to specify the non-native VLANs to be NATed.

Thank you for choosing Cisco,

Christopher Ebert

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Senior Network Support Engineer - Cisco Small Business Support Center

[Romeo Sulzer]

Dear Christopher

Thank you very much for your reply.  Actually what I found out is that starting from firmware version 4.x I need to create a firewall access rule for each additional subnet's IP range.  With the access rules in place, the internet connectivity works now without defining the multiple subnets.

I suppose the multiple subnets I only need if I want to forward ports to one of the non native subnets?

Kind regards,

Romeo