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what does debug outputs mean ?

How are you? Please anybody tell me that what those debug outputs mean,. For example, when I read below debug outputs, I understand that "src" is source, and "dst" is destination.

"debug arp"

*Mar 1 00:06:09.619: IP ARP: creating incomplete entry for IP address: 192.1.1.1 interface Ethernet0/1 *Mar 1 00:06:09.619: IP ARP: sent req src 172.16.39.3 00b0.64cb.eab1, dst 192.1.1.1 0000.0000.0000 Ethernet0/1 *Mar 1 00:06:09.635: IP ARP rep filtered src 192.1.1.1 0010.7b81.0b19, dst 172.16.39.3 00b0.64cb.eab1 wrong cable, interface Ethernet0/1

what is "rep" means ?

Is there any explanation or book or reference about debug output ? It looks complex, and I feel like I'm reading password messages..

Reply to
jh3ang
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Before sending an ARP request, the router creates an entry in the ARP cache for the address it needs to resolve. It's an incomplete entry because it doesn't have the MAC address filled in yet.

Then it sends an ARP request, with the specified source and destination IP and MAC addresses, over interface Ethernet0/1.

It received an ARP reply and filtered it for some reason that it calls "wrong cable". I guess it means that it didn't expect it to be on that interface, but I'm not sure why since it's the same interface it sent it through.

It's weird that the router is ARPing for addresses that aren't in the same subnet as the interface. Do you have a default route pointing to Ethernet0/1?

"req" and "rep" are request and reply.

You can probably find web sites that will explain a few common debug lines, but I don't think there's any complete reference. The assumption is that if you know enough to troubleshoot a network you should be able to figure out what the debug output means.

Reply to
Barry Margolin

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