Dynamic NAT with a pool, then overload it

NetLab lab Intermediate 4 tasks 20 points

The ISP has given the office two more addresses, 203.0.113.3 and 203.0.113.4. R1's inside and outside interfaces are already marked.

Create a pool OFFICE with these two addresses (mask 255.255.255.248) and translate the LAN to it with ACL 10. Try all three PCs.
Two addresses aren't enough for three PCs: add overload to the rule, clear the old translations, and check that all three PCs work.

How it works: this is VulnTech NetLab, a network simulator running in your browser. Click a device in the diagram to open its console and type commands, just like on real equipment (? shows help, Tab finishes a word). Click a cable to inspect it. Tasks tick themselves off as you complete them; questions are answered in the box under each task. Your work is kept if you reload; Reset starts the network over.

Solution explanation

Without overload each PC takes a whole pool address, so the third one has none left and its traffic is dropped. With overload, hosts share the pool addresses by port. Typing the rule again with overload replaces the old one; clearing the translations removes the one-to-one entries still holding both addresses.

Show solution

[R1]
enable
configure terminal
access-list 10 permit 192.168.1.0 0.0.0.255
ip nat pool OFFICE 203.0.113.3 203.0.113.4 netmask 255.255.255.248
ip nat inside source list 10 pool OFFICE
end
[PC1]
ping 198.51.100.10
[PC2]
curl http://198.51.100.10
[PC3]
curl http://198.51.100.10
[R1]
show ip nat translations
configure terminal
ip nat inside source list 10 pool OFFICE overload
end
clear ip nat translation *
[PC1]
ping 198.51.100.10
[PC3]
curl http://198.51.100.10
[R1]
show ip nat translations