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Use private IP on inside interfaces of transit routers

 
 
mliu
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      07-15-2003
What happens if you put private IPs (192.168.x.x) on the INSIDE
interfaces of your internet transit routers.

ISP -- (public IP) Edge Router ( private IP) -- inside network --
(private IP) BGP Router (public IP) -- downstream

1. It wont work at all, it stops passing internet traffic?
2. It passes traffic, but traceroute wont work, skips the hop with
private ip configured?
3. It works well. (doubt about this one)

Thanks for your answer!

 
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Chris
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      07-15-2003

"mliu" <(E-Mail Removed)> wrote in message news:bf1bek$f6g$(E-Mail Removed)...
> What happens if you put private IPs (192.168.x.x) on the INSIDE
> interfaces of your internet transit routers.
>
> ISP -- (public IP) Edge Router ( private IP) -- inside network --
> (private IP) BGP Router (public IP) -- downstream
>
> 1. It wont work at all, it stops passing internet traffic?
> 2. It passes traffic, but traceroute wont work, skips the hop with
> private ip configured?
> 3. It works well. (doubt about this one)
>
> Thanks for your answer!
>


It shouldn't matter as long as the source and destination IP's are live
addresses for any IP traffic crossing the network as long as your routing is
configured correctly and you are advertising the routes correctly. I work
for a comms company / ISP and we use 10.x.y.x addresses on our core network
for many devices.

Chris.



 
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mliu
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      07-15-2003
Thanks Chris. Could you show me what the traceroute looks like from
outside and pass through your netowork to your downstream AS? This
question has been borthering me for awhile...Thanks.

Chris wrote:

> "mliu" <(E-Mail Removed)> wrote in message news:bf1bek$f6g$(E-Mail Removed)...
>
>>What happens if you put private IPs (192.168.x.x) on the INSIDE
>>interfaces of your internet transit routers.
>>
>>ISP -- (public IP) Edge Router ( private IP) -- inside network --
>>(private IP) BGP Router (public IP) -- downstream
>>
>>1. It wont work at all, it stops passing internet traffic?
>>2. It passes traffic, but traceroute wont work, skips the hop with
>>private ip configured?
>>3. It works well. (doubt about this one)
>>
>>Thanks for your answer!
>>

>
>
> It shouldn't matter as long as the source and destination IP's are live
> addresses for any IP traffic crossing the network as long as your routing is
> configured correctly and you are advertising the routes correctly. I work
> for a comms company / ISP and we use 10.x.y.x addresses on our core network
> for many devices.
>
> Chris.
>
>
>


 
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mliu
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      07-15-2003
Great! That makes sense and it is the way that I thought. Thanka alot!!!

Barry Margolin wrote:

> In article <bf1bek$f6g$(E-Mail Removed)>, mliu <(E-Mail Removed)> wrote:
>
>>What happens if you put private IPs (192.168.x.x) on the INSIDE
>>interfaces of your internet transit routers.

>
>
> Strictly speaking it's a violation of RFC 1918, but it's a very common one
> nonetheless. I think @Home used to do it.
>
>
>>2. It passes traffic, but traceroute wont work, skips the hop with
>>private ip configured?

>
>
> Those hops will time out if there's a router along the way back that
> filters packets with private source addresses.
>


 
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Walter Roberson
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      07-15-2003
In article <rHWQa.173$(E-Mail Removed)3.com>,
Barry Margolin <(E-Mail Removed)> wrote:
:In article <bf1bek$f6g$(E-Mail Removed)>, mliu <(E-Mail Removed)> wrote:
:>What happens if you put private IPs (192.168.x.x) on the INSIDE
:>interfaces of your internet transit routers.

:Strictly speaking it's a violation of RFC 1918, but it's a very common one
:nonetheless.

You can make it RFC 1918 compliant by using a little bit of NAT
at the edges of your network -- the criteria is that you must
not let packets with those addresses be routed into the public networks.
--
We don't need no side effect-ing
We don't need no scope control
No global variables for execution
Hey! Did you leave those args alone? -- decvax!utzoo!utcsrgv!roderick
 
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Barry Margolin
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      07-15-2003
In article <bf1ndr$l5a$(E-Mail Removed)>,
Walter Roberson <(E-Mail Removed)-cnrc.gc.ca> wrote:
>In article <rHWQa.173$(E-Mail Removed)3.com>,
>Barry Margolin <(E-Mail Removed)> wrote:
>:In article <bf1bek$f6g$(E-Mail Removed)>, mliu <(E-Mail Removed)> wrote:
>:>What happens if you put private IPs (192.168.x.x) on the INSIDE
>:>interfaces of your internet transit routers.
>
>:Strictly speaking it's a violation of RFC 1918, but it's a very common one
>:nonetheless.
>
>You can make it RFC 1918 compliant by using a little bit of NAT
>at the edges of your network -- the criteria is that you must
>not let packets with those addresses be routed into the public networks.


That'll make for some confusing traceroutes -- you'll see the NAT's address
repeated for each internal router link (assuming you do many-to-1 NAT).
But I guess it's better than lots of timeouts.

--
Barry Margolin, http://www.velocityreviews.com/forums/(E-Mail Removed)
Level(3), Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
 
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