Consolidated Platform Configuration Guide, Cisco Ios Release 15.2(4)E (Catalyst 2960-X Switches - Cisco Catalyst 2960 series Configuration Manual

3 information when applied to fragments. The information in this example is that the packet is TCP and
that the destination is 10.1.1.1.
• Packet B is from host 10.2.2.2, port 65001, going to host 10.1.1.2 on the Telnet port. If this packet is
fragmented, the first fragment matches the second ACE (a deny) because all Layer 3 and Layer 4
information is present. The remaining fragments in the packet do not match the second ACE because
they are missing Layer 4 information. Instead, they match the third ACE (a permit).
Because the first fragment was denied, host 10.1.1.2 cannot reassemble a complete packet, so packet B
is effectively denied. However, the later fragments that are permitted will consume bandwidth on the
network and resources of host 10.1.1.2 as it tries to reassemble the packet.
• Fragmented packet C is from host 10.2.2.2, port 65001, going to host 10.1.1.3, port ftp. If this packet is
fragmented, the first fragment matches the fourth ACE (a deny). All other fragments also match the
fourth ACE because that ACE does not check any Layer 4 information and because Layer 3 information
in all fragments shows that they are being sent to host 10.1.1.3, and the earlier permit ACEs were checking
different hosts.

Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)

Information About Access Control Lists
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