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Cisco Bug: CSCuq26920 - 3850/3650 Access-List not permitting ICMP Fragments

Last Modified

Nov 27, 2020

Products (1)

  • Cisco Catalyst 3850 Series Switches

Known Affected Releases

15.0(1)EZ3 15.2(2)E

Description (partial)

3650 and 3850 switches will drop ICMP Fragments when passing through an access-list with any kind of "deny icmp" statement configured.

Any 3650 or 3850 switches with an access-list applied where there is a "deny icmp" statement before a "permit ip any any" statement will trigger this issue. Specifically the ICMP fragments will be dropped, the initial ICMP packet with header information will check against the access-list correctly.

ICMP Fragments occur when an ICMP frame has to be broken into multiple parts due to MTU settings on nodes on the network.
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