Ip address duplicate with SVI admin down

[YVI@Cisco]

Hi,

Today we had duplicate ip issues between two SVIs with the same ip address ; one SVI was admin down...?

We saw some traffic on the down/down SVI :

#sh int vlan402

Vlan402 is administratively down, line protocol is down , Autostate Enabled

  Hardware is Ethernet SVI, address is 4cbc.48a5.827b (bia 4cbc.48a5.827b)

  Description: Vlan Mgmt

  Internet address is 10.10.10.1/24

  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive not supported

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input 1d10h, output 2d04h, output hang never

  Last clearing of "show interface" counters never

  Input queue: 0/375/0/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 9000 bits/sec, 13 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     146435 packets input, 10955861 bytes, 0 no buffer

     Received 0 broadcasts (0 IP multicasts)

     0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

     555 packets output, 33300 bytes, 0 underruns

     0 output errors, 2 interface resets

     0 unknown protocol drops

     0 output buffer failures, 0 output buffers swapped out

How is that possible ?

thanks in advance.

Regards.

S.

[paul driver]

Hello

Not so sure i understand, Duplicate ip addressing is being reported . so what is the question?

[YVI@Cisco]

Hi Paul,

Thanks for your quick reply.

My question is, how is it possible to have a duplicate ip sourced by an inactive SVI (admin down), and traffic raising on that SVI ?

Thanks,

YVI

[paul driver]

Hello

If the interface is in a admin down state then it possible to manually duplicate an interface address with another and the software will let you do it, The switch/router should complain about it however i think the duplicate addressing will still take.

So that's a possibility for the duplicate, as for the interface stats i see the interface counter haven't been cleared so it is possible your seeing a ghost entry?

Another possible reason it could be a bug has @Georg Pauwen mentioned?

[Georg Pauwen]

Hello,

could be a bug, what platform and what IOS is this happening on ?