Prefix on Nat Pool
As in
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 24
What is it for?
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 24
What is it for?
Comments
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thenjduke
Member Posts: 894 ■■■■□□□□□□
It is the same thing that the netmask does. It identifies what network the pool addresses belong too.CCNA, MCP, MCSA, MCSE, MCDST, MCITP Enterprise Administrator, Working towards Networking BS. CCNP is Next. -
Cyanic
Member Posts: 289
Yes, I get that, but it seems useless in this case. I mean you specify the the start and stop address so what does it matter what the prefix is?
For instance these all do the same thing right?
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 24
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 25
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 26
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 27
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burbankmarc
Member Posts: 460
I don't know. I thought it'd have something to do with the routing table or CEF or something but I just threw a config together and it didn't affect that stuff at all. -
notgoing2fail
Member Posts: 1,138
Yes, I get that, but it seems useless in this case. I mean you specify the the start and stop address so what does it matter what the prefix is?
For instance these all do the same thing right?
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 24
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 25
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 26
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 27
hmmm.....not you've got me thinking..... -
fly351
Member Posts: 360
Yes, I get that, but it seems useless in this case. I mean you specify the the start and stop address so what does it matter what the prefix is?
Just off the top of my head... if your NAT'ing to the internet, wouldn't it be useful to know the network/broadcast addresses of the subnet you are on?CCNP :study: -
Cyanic
Member Posts: 289
Just off the top of my head... if your NAT'ing to the internet, wouldn't it be useful to know the network/broadcast addresses of the subnet you are on?
Yes and those are defined on the interface itself. The NAT pool simply defines a pool of addresses to use for the translation. Since you define the start and stop points of that, it just seems like the prefix is unnecessary. There may be some use for it that I am not aware of though. -
stuh84
Member Posts: 503
At a guess, if the address has a prefix, it could then be filtered with a prefix-list. I'm not sure if thats definitely the case, but its possible I guess.Work In Progress: CCIE R&S Written
CCIE Progress - Hours reading - 15, hours labbing - 1 -
notgoing2fail
Member Posts: 1,138
Yes and those are defined on the interface itself. The NAT pool simply defines a pool of addresses to use for the translation. Since you define the start and stop points of that, it just seems like the prefix is unnecessary. There may be some use for it that I am not aware of though.
Here you go!
The required netmask (or prefix) parameter performs a kind of verification check on the range of addresses. If the address range would not be in the same subnet assuming the configured netmask was used, then IOS will reject the IP NAT POOL command. -
Cyanic
Member Posts: 289
notgoing2fail wrote: »Here you go!
The required netmask (or prefix) parameter performs a kind of verification check on the range of addresses. If the address range would not be in the same subnet assuming the configured netmask was used, then IOS will reject the IP NAT POOL command.
Nice find. Still odd in my book, but good to know. -
notgoing2fail
Member Posts: 1,138
Nice find. Still odd in my book, but good to know.
Well it's very interesting, I suppose the range has to be within a subnet. Sounds like it can't crossover to another network.
