Intergalactic magnetic field strength scan for several different assumed coherence lengths λ_B. The scan is performed via a simultaneous fit of GeV–TeV observations at hand. Calculations with both CRPropa (Alves Batista et al. 2016) and CRbeam (Berezinsky & Kalashev 2016) Monte Carlo codes are presented. Lines of different colours depict the χ² values estimated for different non-zero IGMF strengths. The solid black line represents the case of zero IGMF, in which case the secondary emission dominates in the Fermi/LAT energy range; the dashed black line represents the reference fit with the cascade contribution disabled.