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ARP Broadcasts

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OnoSendai

OnoSendai

Technical User
Jun 18, 2004
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Why would a switch continually send out ARP broadcasts?

I've seen this a couple of times and dont really understand why.

Seems the switch will braodcast a whole range of addresses then repeat the prosess seconds later.

I keep seeing traces with like 30 to 40% ARPs
 
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is it a Cisco Lightstream 1010? If you have host-routing enabled on that product, the Ethernet interface will broadcast excessive ARPs (no known work-around)

Owen O'Neill
Datacom Systems Inc.
Northeastern SE
 
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Is the source of the ARP broadcasts the switch itself or are you just seeing the broadcasts out a switch port? Look at the source MAC address of the broadcasts.

A switch will normally flood ARP broadcasts to every port since he doesn't know which port will answer.

If the source MAC address is another system, then it may be infected with a worm/virus that is looking for another host to infect.

HTH,
Patrick

Patrick Bartkus, CCNP, CNX, SCM, RHCT Sr. Network Engineer
GA Dept of Labor IT Network Services
If truth were not absolute, how could there be justice?
 
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