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Cisco Bug: CSCvs94319 - When use NAT,the packet send to Multicast address will be added additional 12bytes.

Last Modified

Jun 22, 2020

Products (1)

  • Cisco Catalyst 6000 Series Switches

Known Affected Releases

15.5(1.1.49)SY4

Description (partial)

Symptom:
H/W: WS-C6504-E
S/W: 15.5(1)SY4

If PIM and NAT is configured on the same interface then multicast packets might be punted to CPU and forwarded in software switched path
If these multicast frames are small [between 64B and 76B] then these packets will be padded to 76B
Therefor incoming 64B frame will have extra 12B  padding added and will leave the device as 76B frame

Conditions:
ip nat [inside|outside] is configured on the interface
ip pim [sparse-mode|dense-mode|sparse-dense-mode] is configured on the same interface
multicast data traffic arriving on such an interface
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