mean of debug arp message

[tdanetsco]

Hi all,

Can someone tell me what means ?

04:10:38: IP ARP: rcvd rep src 192.168.12.2 0000.0c07.ac02, dst 192.168.12.2 Vlan300

BR,

[Danilo Dy]

Hi,

That's the output of "debug ip arp" I presume.

This means that host 192.168.12.2 received a response from itself. The MAC Address is HSRP virtual MAC address, is this a HSRP virtual IP address?

Regards,

Dandy

[johgill]

a.k.a. GARP

[tdanetsco]

Hi Dandy,

yes, it's a HSRP Virtual IP, but why src=dst ?

BR,

[Richard Burts]

Mustapha

If there was debug ARP running it might be interesting and helpful to see if there was a request for the address that comes before this response. If so the details from the request may help us understand the response better.

It might also be helpful to see how this interface is configured, both its physical address and the HSRP configuration.

It would also be helpful to know if there was possibly a switch of which router was HSRP lead router at the time that this ARP was generated. In a gratuitous ARP both the source address and the destination address are the same and I wonder if that might be what we are looking at.

HTH

Rick

[chschroe]

My guess is that debug output is not from the router sending the grat arp.

NS

[tdanetsco]

Hi,

you can see the diagram for more details, the arp message is produced after pinging the "192.168.12.2" from the switch when the interface Gi0/1 is down and of course no ping reply, this ARP message does not appear when Gi0/1 is UP and i receive ping reply on the switch.

[chschroe]

Actually, that all makes sense really. You requested an arp resolution and it broadcasted the answer back to you.

NS

[chschroe]

Your router received a gratuitous arp message sent with that router's HSRP virtual mac to everyone on that router's SVI Vlan300.

Its basically a broadcast packet that you received that is formed like an arp reply.

NS

[johgill]

Did the interface just come up?

[tdanetsco]

Hi,

no, this debug arp is made on a 2960 switch and from it, i am trying to ping 192.168.12.2 (HSRP VIP configured between two routers).

BR,

[Danilo Dy]

Hi,

I can understand TRUNK between 2 x L3 device, but I don't understand why there is a TRUNK from 2 x L3 device to 2960 Switch since you are using HSRP.

I suspect,Gi0/1 is in blocking mode that's why its down?

Regards,

Dandy

[tdanetsco]

Hi,

i did it with mode ACCESS instead of TRUNK, but the problem was the same, when i make Gi0/1 to DOWN administratively, Gi0/2 does not work.

BR,

[Danilo Dy]

Hi,

If possible, can you post the config of 2 x L3 devices and 2960 switch?

Remove confidential info (i.e. username and password).

If there are public IP address, change the first two octets with A and B

Regards,

Dandy

[johgill]

We may want to re-focus here; what is the noticeable problem?

If there is a problem, was there a time when this network did not have the problem?

Is this gratuitous ARP causing any problems for certain hosts?