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Message from msheiny@seas.upenn.edu

Hello, Saw some e-mails here about Dynamic Arp Inspection (DAI) as a layer-2 defense mitigation for switches - we've been testing this in our own environment and I had some questions that maybe one of you have run into before. I've started seeing issues where some of our HP printers (that are getting static IPs via DHCP) are not obeying their lease-time restriction and checking back into the DHCP server in a timely fashion. This means that consequently they are getting blocked on the switch for some-time until they go out and renew their DHCP lease again. Now we have Brocade devices, not Cisco, but it seems the DAI implementation is pretty similar from what I've read thus far. Has anyone experienced anything like this with network printers + DAI? Thanks for any insight in advance! -- -~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ Michael Sheinberg Network Security Administrator, CETS School of Engineering and Applied Science -~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~ ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.

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Message from jhealy@logn.net

Message from ryan.young@mastersny.org

Jason, Are you using Juniper EX switches? We were having that problem with only our HP printers for about a month and all we ended up doing was restarting the junipers and the problem went away. Not very scientific I know but it ended up working, problem hasn't reoccured in 3 months. Best, Ryan Young Network Administrator The Masters School Dobbs Ferry, NY 10522 On 2/2/12 4:19 PM, "Jason Healy" wrote: >
Message from jhealy@logn.net

On 2/2/2012 3:59 PM, Michael Sheinberg wrote: > I've started seeing issues where some of our HP printers (that are > getting static IPs via DHCP) are not obeying their lease-time > restriction and checking back into the DHCP server in a timely fashion. > This means that consequently they are getting blocked on the switch for > some-time until they go out and renew their DHCP lease again. Now we > have Brocade devices, not Cisco, but it seems the DAI implementation is > pretty similar from what I've read thus far. Not sure about the DAI bits, but we have run into many issues with "marginally competent" DHCP devices. In our case, we are doing dynamic vlan assignments off the MAC address, so when devices on a port change, there may be a delay in "flipping the vlan". Many will only DHCP once at power on, and will not repeat the process with the interface bounces. I haven't tracked to see if they renew but would not be surprised if they did not. They seem to only repeat the process on a hard power-cycle. Jeff ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
Message from ryan.young@mastersny.org

Jason, Wanted to let you know that we had the problem reoccur, but we have change the slp-keep-alive to 1 on the printers and they seem to be staying online. http://h30499.www3.hp.com/t5/Black-and-White/LaserJet-4250-and-4350-Intermi ttently-losing-network-connection/td-p/4986057 Best, Ryan On 2/2/12 8:33 PM, "Jason Healy" wrote: >
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