firewall capture feature packet size Exceed interface default mtu

Felixcao — Tue, 06 Feb 2024 05:26:34 GMT

Customer firewall 3220, version: 10.2.4

Firewall interface mut defaults to ：1500. Jumpo function not enabled。

Question 1: When a firewall receives a TCP packet with a load of 1800 bytes (the df bit of the packet is not set),

I understand that the firewall will fragment the packet into 1500+300 and then forward it. At the same time, when capturing packets on the wall, I cannot catch this 1800 byte packet or 1500 byte packet ?

Is this my understanding correct?

In addition, under the global count statistics

Flow_ Fwd_ MTU_ Exceeded and flow_ipfrag_refrag_mtu These two value of mtu will increase

Is this my understanding correct?

Question 2: When the firewall receives a TCP fragment packet with a load of 1800 bytes (the df bit of the packet is not set), I understand that the firewall will continue to fragment the packet into 1500+300 and then forward it. At the same time, when capturing packets on the wall, it cannot capture this 1800 byte packet or the 1500 byte packet,

Statistics in global count

Flow_ Fwd_ MTU_ Exceeded and flow_ipfrag_refrag_mtu These two value of mtu will increase

Is this my understanding correct?

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firewall capture feature packet size Exceed interface default mtu