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Troubleshooting NAT operation on Loopback Interface or SVI interfaces
I have one question concerning NAT operation. Indeed, i don't understand why when i haven't ip nat inside on loopback interface or SVI interface and i try to do a ping in sourcing on the SVI interface. The nat translate takes effect.
Sample Configuration
interface vlan 3
ip address 10.10.10.1 255.255.255.0! <
whithout ip nat inside on this interface
interface FastEthernet1/0
ip address 212.128.51.1 255.255.255.0
ip nat outside <
with ip nat outside
ip virtual-reassembly
duplex auto
speed auto
--More--
ip nat inside source list NAT-PRIVATE-LAN interface FastEthernet1/0 overload
!
ip access-list standard NAT-PRIVATE-LAN
permit 10.0.0.0 0.255.255.255
R1#ping 212.128.51.2 source vlan 3 """This ping is done without ip nat inside on interface VLAN 3""""""""""""""""""""""""""""""""
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 212.128.51.2, timeout is 2 seconds:
Packet sent with a source address of 10.10.10.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/278/484 ms
R1#
R1#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 212.128.51.1:7 10.10.10.1:7 172.16.8.2:7 172.16.8.2:7
icmp 212.128.51.1:8 10.10.10.1:8 172.16.8.2:8 172.16.8.2:8
icmp 212.128.51.1:9 10.10.10.1:9 172.16.8.2:9 172.16.8.2:9
i had understood that to make the nat translation , there must be have both the nat rule but also IP nat inside and ip nat outside on the relevant interfaces ?
But a PC connected on thé port tagged on VLAN 3 will not be translated without ip nat inside on VLAN 3 ?
Sample Configuration
interface vlan 3
ip address 10.10.10.1 255.255.255.0! <
whithout ip nat inside on this interface
interface FastEthernet1/0
ip address 212.128.51.1 255.255.255.0
ip nat outside <
with ip nat outside
ip virtual-reassembly
duplex auto
speed auto
--More--
ip nat inside source list NAT-PRIVATE-LAN interface FastEthernet1/0 overload
!
ip access-list standard NAT-PRIVATE-LAN
permit 10.0.0.0 0.255.255.255
R1#ping 212.128.51.2 source vlan 3 """This ping is done without ip nat inside on interface VLAN 3""""""""""""""""""""""""""""""""
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 212.128.51.2, timeout is 2 seconds:
Packet sent with a source address of 10.10.10.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/278/484 ms
R1#
R1#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 212.128.51.1:7 10.10.10.1:7 172.16.8.2:7 172.16.8.2:7
icmp 212.128.51.1:8 10.10.10.1:8 172.16.8.2:8 172.16.8.2:8
icmp 212.128.51.1:9 10.10.10.1:9 172.16.8.2:9 172.16.8.2:9
i had understood that to make the nat translation , there must be have both the nat rule but also IP nat inside and ip nat outside on the relevant interfaces ?
But a PC connected on thé port tagged on VLAN 3 will not be translated without ip nat inside on VLAN 3 ?