CCNA Notes
CompTIA LX103
Cisco ICND1
Cisco ICND2
Cisco CCNP Route
Various
Labs
CompTIA LX103
Cisco ICND1
Cisco ICND2
Cisco CCNP Route
Various
Labs
Static NAT requires few configuration steps. Each static mapping between local and global addresses must be configured. Not unlike a static entry for every static IP address required. You must inform the router on which interfaces to use NAT
. Interface subcommands inform the router which interfaces are inside
/ outside
.
ip nat inside
command on an interface to specify inside.ip nat outside
command on an interface to specify outside.ip nat inside source static inside-local inside-global
from global config to configure the static mappings.Create an access list to match a group of source addresses as needed – why else would we overload?
R1(config-std-nacl)#permit 10.1.1.0 0.0.0.255 R1#sh access-lists Standard IP access list NAT 10 permit 10.1.1.0, wildcard bits 0.0.0.255 (2 matches) 20 deny any
Then configure NAT to match against entries in the NAT list configured above. Specify OVERLOAD
to enable PAT.
ip nat inside source list MY_LIST int fa0/0 OVERLOAD
R1#sh ip nat statistics Total active translations: 0 (0 static, 0 dynamic; 0 extended) Outside interfaces: FastEthernet0/0, Serial0/0 Inside interfaces: FastEthernet0/1, Loopback0 Hits: 16 Misses: 2 CEF Translated packets: 18, CEF Punted packets: 0 Expired translations: 2 Dynamic mappings: -- Inside Source [Id: 2] access-list NAT interface FastEthernet0/0 refcount 0 Appl doors: 0 Normal doors: 0 Queued Packets: 0 R1#sh ip nat translations Pro Inside global Inside local Outside local Outside global icmp 2.2.2.1:1 10.1.1.1:1 2.2.2.2:1 2.2.2.2:1 icmp 2.2.2.1:11 10.1.1.3:11 2.2.2.2:11 2.2.2.2:11
Useful with dynamic NAT in the event you run out of dynamic addresses to translate to. Clearing translations will free up slots if the clearout timer isn't quick enough.
R1#clear ip nat translation *
Examine the following show command output on a router configured for dynamic NAT:
-- Inside Source access-list 1 pool fred refcount 2288 pool fred: netmask 255.255.255.240 start 200.1.1.1 end 200.1.1.7 type generic, total addresses 7, allocated 7 (100%), misses 965 Users are complaining about not being able to reach the Internet. Which of the following is the most likely cause?
The NAT pool does not have enough entries to satisfy all requests.
The problem is not related to NAT, based on the information in the command output.
The command output does not supply enough information to identify the problem.
Standard ACL 1 cannot be used; an extended ACL must be used. You answered this question correctly. ×
Explanation: The last line mentions that the pool has seven addresses, with all seven allocated, with the misses counter close to 1000 - meaning that close to 1000 new flows were rejected because of insufficient space in the NAT pool.