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Client 1 & 2 are not able to ping the web server 209.65.200.241, but all the routers & DSW1,2 can ping the server.

NAT problem. (use ipv4 Layer 3)
problem on R1 Nat acl

Configuration on R1
ip nat inside source list nat_pool interface s0/0/0/1 overload

ip access-list standard nat_pool
permit 10.1.0.0
!
interface serial0/0/0/1
ip address 209.65.200.224 255.255.255.252
ip nat outside
!
interface Serial0/0/0/0.12
ip address 10.1.1.1 255.255.255.252
ip nat inside
ip ospf message-digest-key 1 md5 TSHOOT
ip ospf authentication message-digest

Answer:add to acl 1 permit ip 10.2.1.0 0.0.0.255

Ans1) R1
Ans2) NAT
Ans3) Add the command permit 10.2.0.0 in the nat_pool access-list