secondary IP address and routing

Unanswered Question
Dec 2nd, 2009

2651XM eth0 configured with IP address (, secondary IP address ( and connected to fa0/1 on a 3750

3750 has int VLAN100 ( and VLAN 200 ( but without an SVI.  The only way I can get any connectivity is to configure fa0/1 with 'switchport access vlan 200'.  With that in place, from the switch I can ping both router IP addresses.  Workstations on VLAN100 can ping their default gw but cannot ping anything on VLAN200 (servers). Needless to say anything on VLAN200 subnet can't ping the default gw.

Am I doing something wrong?

I would like to be able to route traffic between both subnets using both IP addresses on the 2651 as the default gateways.

The 2651 is provider controlled so getting changes done to it is time consuming.  Getting it to work with this config is desirable but it can be changed if necessary.


I have this problem too.
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Jon Marshall Wed, 12/02/2009 - 13:43


If you have the clients in separate vlans then you should use routing on a stick rather than secondary IP addressing. Secondary IP addressing would be more useful if all clients were in 1 vlan but you wanted them to use different IP subnets.

Have a look at this config example, you will need a minimum of IP Plus feature set on your router -

802.1q router on a stick



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