Why is only R3 performing the Access List?

[JoshGarmonCiscoCCNA]

http://www.informit.com/library/content.aspx?b=CCNA_Practical_Studies&seqNum=76

You'll have to scroll down to the extended part.

Extended Access List

Figure 15-2 shows TWO routers R3 and R5

the scenario is to block certain types of traffic behind both routers.

However, only R3 is doing the access-lists.

This is confusing because the Rules say apply Extended ACLs closest to SOURCE

[Richard Bradfield]

The S0 interface of R3 is where the WAN traffic comes into the site. You want to control traffic to the 192.168.3.0 and the 192.168.50.0 subnets, so S0 on R3 is the obvious place to do it.

[JoshGarmonCiscoCCNA]

Is S0 the "closest to the source" in this particular situation?

When you permit/deny specific kinds of traffic...does that mean FROM or TO those kinds of servers?

[Vinit Jain]

yes, based on the extended ACL, the permit/deny statements have from and to traffic which could be any device in the network. Rest i believe Richard has already explained it.