This article describes the issue of the decrease in the maximum number of sessions, when IPv6 is enabled in the flow mode.

Prior to enabling IPv6, the maximum number of sessions on the SPC for High End SRX devices is:

{secondary:node1}[edit]
root@lab# run show security flow session summary node 1 | match Max

Maximum-sessions: 1048576

root@lab# show security forwarding-options
family {
    inet6 {
        mode flow-based;
    }
}

{secondary:node1}[edit]
root@lab# run show security flow session summary node 1 | match Max

Maximum-sessions: 819200

For SRX platform, the device capacity for IPv6 sessions is 50% of the maximum IPv4 sessions. This due to each IPv6 session taking up two slots out of the session table. When both IPv4 and IPv6 are enabled (flow mode), the session capacity for IPv4 sessions is reduced by 20%.

The following tables lists the session capacity for IPv4 sessions:
 

• IP v4: 409600
• IP v6: 262144

NOTE: "On the newer platforms we do not have memory constrain like earlier and we can accommodate ipv6 sessions. Hence, there will not be any decrease in session count for ipv6."