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Cisco Bug: CSCvs58147 - ASR5500 wrong ipv6 fragments handling with "policy ipv6 tunnel mtu exceed fragment inner"

Last Modified

Jan 13, 2020

Products (1)

  • Cisco ASR 5000 Series

Known Affected Releases


Description (partial)

ASR5500 is double fragmenting ICMPv6 packets, i.e. fragmenting the IPv6 fragments if they are bigger than configured ipv6 MTU (data-tunnel mtu) under APN.

Multiple conditions should be met to face this deffect:

- ASR5500 without VPP (not iCUPS setup). Possible ASR5000 is affected as well.
- APN configured to allow packets bigger than the configured MTU without dropping and sending ICMP packet too big, i.e. "policy ipv6 tunnel mtu exceed fragment inner" configured under APN.
- APN configured with smaller IPv6 MTU (data-tunnel mtu) than the one configured on the peer
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