Multiple IPs in same subnet for a vlan?

[lgreco215]

I have a 9300 series switch configured with multiple Vlans, each of which has an IP address of x.x.x.254 255.255.255.0  These .254 IP addresses are used as the gateway address for devices connected to the vlan and routing is working nicely. We have control of the configuration for all devices except one which has X.X.X.1 as its defined gateway.  We need to route the traffic bound for X.X.X.1 as though it was bound for X.X.X.254 for proper routing to the rest of the network. I know how to do it if the .1 were in a subnet not already defined in the switch, but since it's in the same subnet I'm at a loss.

Vlan 101:  10.10.1.0/24,   IP 10.10.1.254 255.255.255.0

Client device static IP: 10.10.1.196 255.255.255.0   Gateway: 10.10.1.1

The gateway needs to be 10.10.1.254 but we have no way to alter the client.

Is there any way to configure this on a 9300 series switch so packets addressed to 10.10.1.1 behave as though they were addressed to 10.10.1.254?

[balaji.bandi]

we can understand the situation.

1. i would check how many active devices in the network of the subnet

2. if possible  make a subnet and add secondary IP 10.10.1.1 and primary IP 10.10.1.254

That's the only option I can think of.

There are other options but it's over-engineering like VRF..bla bla...(I will not go that route).

[Georg Pauwen]

Hello,

if Vlan101 already exists, I would agree that adding a secondary IP address (10.10.1.1/24) should work:

interface Vlan101
ip address 10.10.1.1 255.255.255.0 secondary
ip address 10.10.1.254 255.255.255..0

You can route anything external towards that secondary IP address as well...

[lgreco215]

I'll look into using the secondary IP for the vlan.  I thought it wouldn't work because the address is already consumed by the initial address space.

There are maybe two dozen devices on the vlan. Re-IPing those devices is possible, but not optimal as they are expected to be up 24/7 with minimal maintenance windows. To complicate things, the vlan is spread across 3 switches connected with trunks, although the .1 address currently only needs to talk to the .254 devices on the same switch. 

[balaji.bandi]

Since you mentioned this was stretched multiple switches and trunks.

if the IP is free 10.10.1.1, then where is the device connected? create an SVI with the same VLAN and add IP address on the switch, so the device connects to 10.10.1.1

So example ;

main Switch vlan X have 10.10.1.254,

device connected switch has vlan x 10.10.1.1

is this work for you?

[lgreco215]

The .1 device connects to the main switch, and that switch needs to remain as .254.  I may be able to change the vlan IP of one of the other switches to be .1 and the established routes should still work. There are only a few devices on that subnet on the switch I'm considering changing and there's only one route entry that affects that address range.  I'll model it out with Packet Tracer and see if behaves as expected.  Nice option BB.

[balaji.bandi]

It does not matter which switch is having .1 IP, as long as the trunk is allowed that VLAN, the device can reach .1 your problem will be solved. please test and advise.