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I have inherited a network and I don’t understand why the VLAN’s are setup this way.

I have 6 cisco switches with a single Internet gateway. My clients are all on the VLAN 1 with an IP of 10.60.15.x/18. Their gateway is set to be My gateway has an internal IP of but on VLAN100 (note the different subnet mask). The core switch connected to the gateway has VLAN IP’s of and so that all Internet traffic is switched through this core switch.

Is there an advantage to having my Internet Gateway on a separate VLAN? I’ve never seen this before. Is the setup advanced or just overly complex?

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Are you sure no equipment is sharing that subnet or vlan with the gateway, that it's just the gateway alone there? – Bart Silverstrim Mar 24 '11 at 20:13
The gateway seems to stand alone. There is only one switch port that is configured on VLAN100 and it is direclty connected to the internal NIC on the gateway. – Peter S. Mar 24 '11 at 20:23
up vote 0 down vote accepted

I always prefer a small VLAN for the network device peering, that way you get a real routing jump and not a redirect if your router reroutes to a different device on the same VLAN as the access nodes.

There are other advantages, such as you can have ACL's in the switch if required, you don't need to send out routing protocol messages on that VLAN (if you use OSPF/BGP/EIGRP etc), keeps things cleaner.

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