![]() ![]() Currently, NAT enables and disables VFR internally that is, when NAT is enabled on an interface, VFR is automatically enabled on that interface. VFR is designed to work with any feature that requires fragment reassembly (such as Cisco IOS Firewall and NAT). If the IP datagram does not receive all of the fragments within the specified time (which can be configured via the timeout seconds option), the timer will expire and the IP datagram (and all of its fragments) will be dropped. Feature History for Virtual Fragmentation Reassembly Release 12.3(8)T Modification This feature was introduced. In addition to configuring the maximum threshold values, each IP datagram is associated with a managed timer. Virtual fragmentation reassembly (VFR) enables the Cisco IOS Firewall to create the appropriate dynamic ACLs, thereby, protecting the network from various fragmentation attacks. The max-reassemblies number option and the max-fragments number option allow you to configure maximum threshold values to avoid a buffer overflow attack and to control memory usage. The topology and configurations for this example are shown below: R1: interface FastEthernet0/0 ip address 10.1.1.1 255.255.255.0 interface Serial0/0 ip address 10.0.12.1 255.255.255.0 ip route 0.0.0.0 0.0.0.0 Serial0/0 R2: interface Serial0/0 ip address 10.0.12.2 255.255.255. ![]() Here’s what it does:Ī buffer overflow attack can occur when an attacker continuously sends a large number of incomplete IP fragments, causing the firewall to lose time and memory while trying to reassemble the fake packets. How does a service provider manage to allow overlapping IP addresses for its different customers, specifically private IP addresses, without affecting. I got a question from one of my manager what are the pros and cons of ip virtual-reassembly. ![]()
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