A lot of the White's problems were because of their inability to take the larger cities. The industrial cities were the bedrock of the Soviet state – where their support was strongest and ideologically central to them – so defending them was both militarily and politically important. The Soviets realised this quite quickly, and soon started to deliberately fortify their major cities as soon as they were threatened.
The Cossacks Hosts, in particular, could sweep across the steppes, but could not take the major cities. On multiple occasions the Don host failed at Tsaritsyn, the Urals host at Uralsk and the Orenburg host against Orenburg City. On each occasion a successful campaign was ended by an unsuccessful siege.
The only White army consistently able to take such fortifications with success were the AFSR and Wrangel's Russian Army. This was where the Allied tanks and other equipment really came into its own.
It seems about 45 Fortified Areas were designated in the civil war. The first in December 1918 was Astrakhan. At various times others I have seen listed included: Vyatsk, Kazan, Sarapul, Chelyabinsk, Kokchetavsk, Akmolinsk, Simbirsk, Ufa, Perm(?), Troitsk, Samara, Saratov, Orenburg, Sterlitamak, Verkhneuralsk, Zverinogolovsk, Penza, Yekaterinburg, Uralsk, Akmola, Aktobe, Orenburg, Troitsk, Yekaterinoslav, Kiev, Kamyshin, Kursk, Tula, Voronezh, Tambov, Bryansk, Lgovsk, Orlovsk, Yeletsk, Kozlovsk, Outer Moscow, Tambov, Petrograd, Krasnogorsk, Yeisk, Yekaterinodar, Odessa, Murmansk, Arkhangelsk and Kerch.
Fortified Areas in the Civil War from the Soviet Military Historical Journal, 1988
This article discusses the official regulations for the fortified areas.
A look at how one city failed miserably to follow the official regulations.