Skip to main content
  • Place orders quickly and easily
  • View orders and track your shipping status
  • Enjoy members-only rewards and discounts
  • Create and access a list of your products
  • Manage your Dell EMC sites, products, and product-level contacts using Company Administration.

Dell Configuration Guide for the S4048–ON System 9.14.2.6

PDF

IP Fragment Handling

Dell EMC Networking OS supports a configurable option to explicitly deny IP fragmented packets, particularly second and subsequent packets.

It extends the existing ACL command syntax with the fragments keyword for all Layer 3 rules applicable to all Layer protocols (permit/deny ip/tcp/udp/icmp).
  • Both standard and extended ACLs support IP fragments.
  • Second and subsequent fragments are allowed because a Layer 4 rule cannot be applied to these fragments. If the packet is to be denied eventually, the first fragment would be denied and hence the packet as a whole cannot be reassembled.
  • Implementing the required rules uses a significant number of CAM entries per TCP/UDP entry.
  • For IP ACL, Dell EMC Networking OS always applies implicit deny. You do not have to configure it.
  • For IP ACL, Dell EMC Networking OS applies implicit permit for second and subsequent fragment just prior to the implicit deny.
  • If you configure an explicit deny, the second and subsequent fragments do not hit the implicit permit rule for fragments.
  • Loopback interfaces do not support ACLs using the IP fragment option. If you configure an ACL with the fragments option and apply it to a Loopback interface, the command is accepted but the ACL entries are not actually installed the offending rule in CAM.

Rate this content

Accurate
Useful
Easy to understand
Was this article helpful?
0/3000 characters
  Please provide ratings (1-5 stars).
  Please provide ratings (1-5 stars).
  Please provide ratings (1-5 stars).
  Please select whether the article was helpful or not.
  Comments cannot contain these special characters: <>()\