Connecting WAN Network's Conflict IP Address

[amer hanifi]

Hello everyone

I am trying to connect two wan network by L3 cisco switch 

There are duplicate addresses in the two networks that cause devices to fall (IP conflict)
What is the best solution to block conflicting IP Addresses range ?
I have applied the Access Control List to deny the conflicting IP range but the broadcast still goes through the network and fail the devices

Note that I cannot change the IPs of the devices

there is no router in the network 

All the switches in networks are L2 not configured Switches 

[Kasun Bandara]

Hi,

can you share small diagram about how your connected devices? normally you cannot have same address for 2 devices in L2 network (unless using VLANs). also in routers you cannot add same network for 2 interfaces. you have few options.

1. change IP addresses

2. configure VLANs (will not be able to do inter vlan routing if same network)

3. use another L3 device between ISP 2 and switch to create new network.

[amer hanifi]

Hi Casun and thank you for your support

please see the diagram below

 

[Martin L]

First of all, technically speaking I see 2 LANs not WANs, once you add routers that connect 2 LAN via ISP, you can call it WAN network.  So, no L3 between 2 LANs makes it 1 continuous domain, hence IP subnet conflicts.  You can use different vlans in those 2 LANs; aka same subnet but in 2 different vlans but it is more common to use 1 subnet x per 1 vlan x; so I would add L3 devices like a router or a L3 switch between those 2 LANs.  you will need at least 2 L3 devices. i.e. your network A (192.168.1.x/24) on left side is connected via another subnet, let say 10.0.0.0/24 then you connect same subnet 192.168.1.x/24 on right side.  this is usually done by network topo looking smtg like

PCA <>L2<>L3<>L3<>L2<>PCB where PC A and PCB have the same IP.  (btw, L3<>L3 is WAN in that example)

you can attach your PT file here (in a zip format).  some1 usually will fix it.

Regards, ML
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