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Some Cisco Pix 515, 515-DC and 506 Firewalls have suffered system hangs when traffic on the network becomes too heavy, requiring a manual restart for the firewall manually, Cisco reported on 18 October.
Cisco expects the problem to occur most often in the 515 models, which are designed for corporate central offices, but said it may also happen in 506 units. The 506 is designed for branch offices, which tend to experience lower traffic levels.
The firewalls are typically installed between a company's internal network and the Internet to guard against intrusion. The flaws can cut off an Internet connection that runs through a firewall, but will not cause a connection to become insecure, Cisco said. Officials at the company were not available to comment in detail about the problem.
While the failures do not pose a security issue, they could cause network availability headaches for a number of large corporations. Cisco holds about one quarter of the overall firewall market, according to Gartner analyst Richard Stiennon.
Cisco has traced the source of the problem to a component that the networking giant began buying from a new supplier in May. The component's timing is slightly different from that on previous units, and the difference makes the system unstable, according to Cisco. Units made after 2 October do not have the flaw.
Cisco is replacing the firewalls for registered customers, free of charge. However, because the replacement units need to come from the company's manufacturing facilities in California, instead of local service centres, service agreements for overnight replacement cannot be met, especially from outside the US.
The only workaround Cisco offers is to reduce the traffic load by hard-coding all the firewall's interfaces to 10Mbps, or making a change elsewhere in the network that reduces traffic to that level. The units most often hang when traffic exceeds 15Mbps, although the threshold varies, according to Cisco. The devices are available with 10Mbps, 100Mbps or 1Gbps interfaces.
Few enterprises are equipped to deal with a workaround that would throttle down a critical network connection so dramatically, Stiennon said. However, only a small percentage have Internet connections of more than 10Mbps, he added.
Cisco also reported a flaw in the way power supplies are attached to motherboards in some Pix 506 Firewalls. Over time, friction and vibration can work the power connection loose, causing the firewall to freeze or reboot, according to the company. A cable tie-down was introduced on 2 October that will keep the power supply attached.
Cisco is replacing the affected 506 units for registered customers, free of charge. As a workaround, Cisco provides instructions on its Web site for opening the firewall and reinserting the power connector in the motherboard.
The failures and possible long waits for replacements put the spotlight on one problem with integrated hardware-software "appliances" such as the Pix Firewalls, Stiennon said. If hardware problems befall a software firewall, such as one from Check Point, most users can solve them easily and quickly by replacing the Intel-based PC on which the software runs.