This is where it gets into the crapshoot that is 1v1 with BVR missiles inside 10 miles. Until 7 miles or so, you stll have a fairly good chance to outright defeat the missile by performing an aggressive max G/ over G exit. Otherwise your only real hope is to chaff and pull G out of plane of the missile. IE the typical barrel roll around the missile. Keep in mind your best bet is to defeat his radar with the notch so he loses his lock and has to reacquire. Thats what the whole Split-S is for, to get out of his initial Radar elevation while you were in the notch, making him have to change his system to reacquire. Giving you time to close the range and get a shot off.
Realistically 1 V 1 Eagle V flanker in DCS the Flanker is at a straight up disadvantage and any time you go closer than 10 miles while spiked It is all a crapshoot and there are no good answers other than try to survive.
Now I have specifically stayed away from talking about taking pre-emptive shots to force him defensive because with non active missiles that you have to support there is not much point to take shots outside of 15NM.
Practice notching, only practice notching the enemies radar, because if you are trying to notch the missile, well good luck with that. It may or may not work, but thats a lot lot harder than notching the jets radar.
Finally the real world answer if the flanker wanted to live in this situation, is if you are spiked through the notch. Leave. You can outrun him you are not in what we call a stern WEZ (no missile in DCS right now can chase you down from ten miles with full burner at any altitude). This is the decision making part of it. Do you elevate your risk by trying to BFM his missiles while all he has to do to shoot you is hit the pickle button? Or do you just run for the nearest friendly and make the guy running you down deal with two angry flankers instead of one.
These are the tough choices 
Ive done tests with this with NB 1v1 and with a good Notch and a rapid dive to the floor I can consistently close the distance to a WVR merge or target him and have him unable to reacquire, and this with me telling him what I’m doing. Done right it can be very very effective. Against a person. The AI is a different story, but the mechanics of the radars and missiles are the same.
Small addition for the Split S to the floor, remember with the Split S you actually can go into the notch 3 times, part of why its so effective. First when you initially notch, second in the split S when you are p ointed Straight down (vertically notching instead of horizontally, still works the same) and third as you pull through the bottom if you do a pure 180 split S you should end up still in the notch. So you have three chances to lose him in this maneuver.
Caveat to all of this for future reference. This is all valid for DCS as of October 2017. If/when the Missile FM’s get updated, if they become more realistic/ the Guidance laws get better, all of this is subject to change. many of the principles will remain the same but the ranges you do them at and what options you have available could all change. IE if R-27ER’s have a better guidance law/ flight model it may be better to take pre-emptive shots at max range to force the opponent on the defensive. But as of right now its just a good way to waste a missile.