Updated iRule for radius called-station-id attribute 31 (persistence)

Hello Ed3, I've configured radius persistence on a customer last year without need for an iRule.

There's persist option available in RADIUS type traffic profile. 

Other than that, you'll need an universal persistence profile that enables cross-service persistence (used for accounting/authentication persistence on same server). 

ltm persistence universal /Common/radius_xsvc {
    app-service none
    defaults-from /Common/universal
    match-across-services enabled
    timeout 300
}
ltm profile radius /Common/radiusLB_31 {
    app-service none
    clients none
    defaults-from /Common/radiusLB
    persist-avp 31
}

Apply both profiles in both your VS's for auth/acc. 

Also, check this link: https://support.f5.com/csp/article/K52316490