The Citizens' rewarded for finishing top of their group is a two-legged affair against the 13-time European champions, with the first leg set to take place at the Santiago Bernabeu.
Guardiola was involved in a few heated El Clasico during his time with FC Barcelona, where he registered nine wins in 17 matches against fierce rivals Los Blancos.
"Real Madrid are a top side, no doubt so it's a difficult draw as Madrid have won this competition 13 times so they are the best in the history of the competition," Begiristain told Sky Sports.
"Though they were second in the group we know their history in this competition, but if you want to be the best, you have to beat the best.
"The best way to start that is with Real Madrid. It's always a pleasure to go and play against Real Madrid and also to play in the Bernabeu.
"We are happy to go there, and we know what we will face.
"They also know us, they know our manager, but it is a real pleasure to go there."