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Beginner

Ip address duplicate with SVI admin down

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.

4 REPLIES 4
VIP Advisor

Re: Ip address duplicate with SVI admin down

Hello

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



kind regards
Paul

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It will hopefully assist others with similar issues in the future
Beginner

Re: Ip address duplicate with SVI admin down

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

Highlighted
VIP Advisor

Re: Ip address duplicate with SVI admin down

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?



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future
VIP Mentor

Re: Ip address duplicate with SVI admin down

Hello,

 

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

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