Problem configuring default route

[TravellingTechie]

I have an SG300-20 configured with 4 vlans, 1, 10, 20, 30. It is configured for L3.  I use this for my home lab network.  VLAN 1 is connected to my cable modem, and gets it's IP address and gateway via DHCP.  I have a host on VLAN 10, and a host on VLAN 20.  I can ping from one host to the other host just fine.  I can ping from the switch to the hosts, and from the switch to the cable modem and internet.  I cannot ping from either of the hosts to the cable modem or internet.

Here is the relevant switch config (IPs masked):

#sh ip int

    IP Address         I/F       Type     Directed   Precedence   Status

                                          Broadcast

------------------- --------- ----------- ---------- ---------- -----------

76.xxx.xxx.xx/20    vlan 1    DHCP        disable    No         Valid

192.168.10.1/24     vlan 10   Static      disable    No         Valid

192.168.20.1/24     vlan 20   Static      disable    No         Valid

192.168.30.1/24     vlan 30   Static      disable    No         Valid

#sh ip route

Maximum Parallel Paths: 1 (1 after reset)

IP Forwarding: enabled

Codes: > - best, C - connected, S - static

S   0.0.0.0/0 [1/2] via 76.xxx.xx.x, 21:43:15, vlan 1

C   76.xxx.xx.0/20 is directly connected, vlan 1

C   192.168.10.0/24 is directly connected, vlan 10

C   192.168.20.0/24 is directly connected, vlan 20

C   192.168.30.0/24 is directly connected, vlan 30

It would appear that the switch is routing between all VLANs except VLAN 1.   Any ideas what I am missing here?

[Tom Watts · Accepted solution]

Hi Brandon, I think the problem is you're expecting NAT to work. It feels like to me VLAN 1 has the internet connection and you're trying to put the other 3 VLANs on the internet.

In theory you're right on but without NAT this cannot work. The switch also does not support NAT.

-Tom
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[TravellingTechie]

Yep you are absolutely right and now I feel like an idiot.  The source IP never gets changed, and the gateway device has no route back.  I knew it was going to be something simple I had overlooked.  Time to go set up a VM to do the NAT.

Thanks,
Brandon