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ICMP Stateful

Hi,

Most of us knows that ICMP is not a stateful protocol, and we can make it using ICMP inspection in ASA.

As per my understanding,

In TCP, TCP Flags are making TCP capable of stateful protocol, In UDP, src and dst port numbers playing the role to make it stateful.. But what makes ICMP to become stateful!!!

Regards,

Manu B.

1 REPLY
Cisco Employee

Re: ICMP Stateful

The ASA builds a ICMp connection for the icmp echoes that is sees. It creates a session based on the identification/sequence number of the icmp header, it's source and destination ip addresses and its type and code. So, it knows what the icmp reply for that packet will look like and it will allow the return traffic.

I hope it clarifies it.

PK

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