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Cisco Bug: CSCur77743 - ICMP packets generated by the router are wrongly NATted

Last Modified

Feb 16, 2018

Products (1)

  • Cisco ASR 1000 Series Aggregation Services Routers

Known Affected Releases


Description (partial)

The clients don't receive ICMP message for the packets dropped by the router NATting the traffic.
This breaks a few things like PMTUD.
The router doing the NAT also shows the following message : 
ICMP: unreachable packet's src is not one of ours?

The issue is seen when the following two conditions are met : 
1) Packet is dropped at "nat outside" interface by the router.
2) Dynamic overload NAT is being used (either pool overload or interface overload).
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Bug Details Include

  • Full Description (including symptoms, conditions and workarounds)
  • Status
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