NVI0 got wrong address

Answered Question
Sep 10th, 2008
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Hello there,


i hope someone knows this better than me:


I have sometimes the "wrong" address on the NVI0 Interface. i use the "old" nat configuration with nat inside and nat outside. sometimes the address of the nvi is the one from a local loopback (then everything works, like ospf between two routers) and the next router has the outside interface address on the nvi. how is this decision made?

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NVI0 is up, line protocol is up

Interface is unnumbered. Using address of Loopback10 (10.51.2.10)

Broadcast address is 255.255.255.255

MTU is 1514 bytes

Helper address is not set

Directed broadcast forwarding is disabled

Multicast reserved groups joined: 224.0.0.5

Outgoing access list is not set

Inbound access list is not set

Proxy ARP is enabled

Local Proxy ARP is disabled

Security level is default

Split horizon is enabled

ICMP redirects are always sent

ICMP unreachables are always sent

ICMP mask replies are never sent

IP fast switching is disabled

IP fast switching on the same interface is disabled

IP Flow switching is disabled

IP CEF switching is disabled

IP Null turbo vector

IP multicast fast switching is enabled

IP multicast distributed fast switching is disabled

IP route-cache flags are Fast, CEF

Router Discovery is disabled

IP output packet accounting is disabled

IP access violation accounting is disabled

TCP/IP header compression is disabled

RTP/IP header compression is disabled

Policy routing is disabled

Network address translation is disabled

BGP Policy Mapping is disabled

WCCP Redirect outbound is disabled

WCCP Redirect inbound is disabled

WCCP Redirect exclude is disabled


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NVI0 is up, line protocol is up

Interface is unnumbered. Using address of FastEthernet0/0 (87.193.***.***)

Broadcast address is 255.255.255.255

MTU is 1514 bytes

Helper address is not set

Directed broadcast forwarding is disabled

Outgoing access list is not set

Inbound access list is not set

Proxy ARP is enabled

Local Proxy ARP is disabled

Security level is default

Split horizon is enabled

ICMP redirects are always sent

ICMP unreachables are always sent

ICMP mask replies are never sent

IP fast switching is disabled

IP fast switching on the same interface is disabled

IP Flow switching is disabled

IP CEF switching is disabled

IP Null turbo vector

IP multicast fast switching is enabled

IP multicast distributed fast switching is disabled

IP route-cache flags are Fast, CEF

Router Discovery is disabled

IP output packet accounting is disabled

IP access violation accounting is disabled

TCP/IP header compression is disabled

RTP/IP header compression is disabled

Policy routing is disabled

Network address translation is disabled

BGP Policy Mapping is disabled

WCCP Redirect outbound is disabled

WCCP Redirect inbound is disabled

WCCP Redirect exclude is disabled


--------------------------------------


thanks in advance

Correct Answer by singhsaju about 8 years 9 months ago

NVI is a new feature in IOS 12.3 and later.

It is enabled by using "ip nat enable " on interfaces and we do not use "ip nat inside" or "ip nat outside" .


If you want to understand how translation and routing differs in the implementation check following link :


http://blog.internetworkexpert.com/2008/02/15/the-inside-and-outside-of-nat/

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singhsaju Wed, 09/10/2008 - 06:48
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Hello,


NVI is enabled and it takes ip address from the interface under which you configure "ip nat enable"


in your first example if you check you should see "ip nat enable" under interface loopback10 and for second example under interface FastEthernet0/0 .


Also check follwoing link:

http://www.cisco.com/en/US/docs/ios/12_4t/ip_addr/configuration/guide/htaddrs.html#wp1084652


HTH

Saju

Pls rate if it helps

martinsp85 Wed, 09/10/2008 - 22:50
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I found this document before, but i did not use the "ip nat enable".

It is a 12.4-15T7 image.

I have used the ip nat outside and inside command.

can you explain me how this interface nvi is used? i did not get it i think.

Correct Answer
singhsaju Thu, 09/11/2008 - 05:38
User Badges:
  • Silver, 250 points or more

NVI is a new feature in IOS 12.3 and later.

It is enabled by using "ip nat enable " on interfaces and we do not use "ip nat inside" or "ip nat outside" .


If you want to understand how translation and routing differs in the implementation check following link :


http://blog.internetworkexpert.com/2008/02/15/the-inside-and-outside-of-nat/

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