Switched network

Unanswered Question
Mar 14th, 2008

What happens if the firewall inside interface and a networked printer are unbeknownstly given the same static IP address? The above happened. The network ;melted down'. The digital phone going P2P to HQ degraded as the day went on--low band width mssg displayed on the phone console. I have to give a report to the IT Director. I would appreciate any insight.

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Richard Burts Fri, 03/14/2008 - 08:29

Said

If there are 2 devices that have been assigned the same IP address then when some device ARPs it will get 2 responses. So sometimes the device ARP table might contain the MAC of the firewall and sometime it might contain the MAC of the printer. The result is that sometimes traffic intended for the firewall gets sent to the firewall as it should but sometimes it would get sent to the printer which would drop it. And sometimes print data would be sent to the printer where it can print and sometimes print data would be sent to the firewall where it would be dropped.

HTH

Rick

saidfrh Fri, 03/14/2008 - 09:17

Rick,

There was a big melt down. I was told the ASA5505 was hot to touch. 1. Can you look into the configs? 2. do you know the commands in the ASA to exclude IPs.

We are transitioning the present architecture: P2P, Branch Office (bo)router>T1>HQ router. The bo accesses the servers and Internet through P2P to hq.

New design: Internet>Cisco 1721 DIA router>ASA5505 firewall>LAN switch>P2P Cisco 1721 router>hq router> servers.

The digital phone system connects the bo with hq through the P2P.

Thamks.

Said

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