Misconfiguration leads to IP Address conflict

[snarayanaraju]

Hello All - When a SVI is created with the IP address that is already configured in another SVI lying in another switch, both SVI is going down because of IP address conflict. Example as  below

SWITCH 1: 

interface vlan 28

   ip address 192.168.1.1 255.255.255.0

SWITCH 2:

interface vlan 50

  ip address 192.168.1.1 255.255.255.0

Is there a way to prevent one SVI not impacted by the other SVI because of these kind of IP address misconfiguration/Confict?

SAIRAM

[Jon Marshall · Accepted solution]

There isn't really a way because the network admin should know what IP subnets are in use and check before assigning the same IP subnet to a different vlan on a different switch.

The above configuration is basically trying to assign two different vlans to the same IP subnet and this won't work unless they are completely separate networks.

You should know which IP subnets are in use and what vlans those IP subnets are used for.

Jon

[snarayanaraju]

Thanks Jon.

Is there a way to avoid these IP overlapping/Conflict human mistakes while assigning IP address to the SVIs of the switches. By chance, the same IP address is used twice, can the switches be intelligent enough to suppress the newly configured IP address / SVI so that existing SVIs will not be impacted?

Generally, we Network Engineers, do PING test before assigning a IP address to SVI. Is there a way on switch level to avoid bringing the network down by wrongly configuring the used IP address?

Thanks in advance 

[Jon Marshall · Accepted solution]

Switches don't have any automatic means of working that out as far as I know.

You really should have a spread sheet at least that documents what IP subnets are in use on your network to avoid these sort of mistakes.

Ping is one way of testing, another is to check the IP routing tables although if you are summarising it isn't always obvious which IP subnets are actually being used.

Detecting duplicate client IPs is possible but I think the assumption with the network devices is that if the engineer is configuring a L3 interface with an IP address he knows that IP subnet is not already being used on the network.

Like I say, keeping an up to date document as to which IP subnets have been allocated and which are in use is a good approach for a large network.

Jon