Duplicate IP address in between HSRP pair with Static NAT

[ktwaddell]

Hi Guys,

Not sure if in the right group here, but I've been upgrading old 2811 with ISR4331's, this one solution runs HSRP on the client facing side with matching static NAT entries, no problem till i upgraded both routers, currently had to roll back 1 of the router upgrades to stop the error.

Config was kept the same, no changes made and only does it with both routers upgraded.

running 15.5(3) S5

I do have another client with a similar solution but there is a small difference on the client facing interfaces

New routers that works has 

Standby use-bia

New routers that error has

IP virtual-reassembly

Sadly not in a position to just 'try' and have to put the new solution forward in the change.

Any ideas guys?

Thanks

Kev 

[Deepak Kumar]

Hi,

I didn't get your question. Please share error message and configuration. 

Regards,

Deepak Kumar

[ktwaddell]

Hi,

Sorry my question is any idea why I'm getting duplicate ip address errors messages once these routers are BOTH upgraded with the same configs?

sorry I missed out the duplicate IP address are static NATs, so router A has errors that 192.168.1.1 is a duplicate ip address with the mac address of router b, and router b has the same errors but with the mac address of router a

I don't have a copy of the error message, it was just a duplicate ip address error  

sorry I cant post the config, but here is the client facing interface

interface GigabitEthernet0/0/1
 description **** Connection to client LAN ****
 ip address 192.168.1.147 255.255.255.240
 ip nat outside
 ip access-group E-EXPERIAN-IN in
 standby 1 ip 192.168.1.145
 standby 1 priority 110
 standby 1 preempt
 standby 1 track 1 decrement 15
 standby 2 ip 192.168.1.148
 standby 2 priority 110
 standby 2 preempt
 standby 2 track 1 decrement 15
 load-interval 30
 speed 100
 no negotiation auto
 no cdp enable
 ip virtual-reassembly

[Samer R. Saleem]

A good help would be posting #show standby brief   output

you might have the two devices not seeing each other and both of them acting like active and duplicate is happening since you will see Virtual IP from two different devices.

[ktwaddell]

Hi,

No the 2nd router was standby while primary was active, they can see each other.

thanks

[Deepak Kumar]

Hi,

Please share an output form both router

show standby 

show ip interface brief

 And If possible, also add a network diagram.

Regards,

Deepak Kumar

[ktwaddell · Accepted solution]

So managed to sort it via TAC case, even though the config hadnt changed and been the same for the last 12 years, the upgraded hardware and IOS forces the error.

Any incoming static NAT address that's also within the interfaces own subnet and running HSRP created a duplicate IP address error, the way round it is to put a no-alias at the end of those static NAT commands

thanks 

[Pascal Douce]

Thanks a lot! Very useful!