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uk.comp.home-networking (UK home networking) (uk.comp.home-networking) Discussion of all aspects of computer networking in the home, regardless of the platforms, software, topologies and protocols used. Examples of topics include recommendations for hardware or suppliers (e.g. NICs and cabling), protocols, servers, and specific network software. Advertising is not allowed.

SNMP and external IP



 
 
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  #1  
Old December 30th 04, 01:07 PM posted to uk.comp.home-networking
Dave J
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Posts: 321
Default SNMP and external IP

Is there any way to use SNMP to acquire the external IP address of a NAT
router?

I'm after persuading my (homemade) dynamic dns client to function over the
NAT link, and short of abusing the system by auto-updating every five
minutes, or using an external host, I can't think of a way to do it.

The only thoughts I've had have been DHCP (apparently no good by my
reading anyhow) or SNMP.

I'm capable of writing my own agent/client for any useable protocol.

Any clues?

Dave J.
  #2  
Old December 30th 04, 02:24 PM posted to uk.comp.home-networking
Alex Fraser
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Posts: 553
Default SNMP and external IP

"Dave J" wrote in message
...
Is there any way to use SNMP to acquire the external IP address of a NAT
router?


Yes. snmpwalk starting at 1.3.6.1.2.1.4.20.1.1 lists all IP addresses on my
router.

See http://www.ibr.cs.tu-bs.de/cgi-bin/sbrowser.cgi

HTH,
Alex


  #3  
Old December 30th 04, 03:05 PM posted to uk.comp.home-networking
Alex Fraser
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Posts: 553
Default SNMP and external IP

"Alex Fraser" wrote in message
...
"Dave J" wrote in message
...
Is there any way to use SNMP to acquire the external IP address of a
NAT router?


Yes. snmpwalk starting at 1.3.6.1.2.1.4.20.1.1 lists all IP addresses on
my router.

See http://www.ibr.cs.tu-bs.de/cgi-bin/sbrowser.cgi


To expand a little, OIDs under the above should have corresponding ones with
the interface index under 1.3.6.1.2.1.4.20.1.2. AIUI it's permissable for an
interface index to change when the system is reinitialised, but IME that
doesn't happen unless the hardware is changed, and that won't happen in a
router. So, as a one-off, you can manually find the interface index for the
router's WAN port. Then (in your DNS update client) you can poll (walking
....1 and ...2) to find the address associated with that interface.

That said, it's undoubtedly easier and probably satisfactory just to walk
the address entries looking for a routable address.

Alex


  #4  
Old January 10th 05, 11:33 AM posted to uk.comp.home-networking
Dave J
external usenet poster
 
Posts: 321
Default SNMP and external IP

In within uk.comp.home-networking,
'Alex Fraser' wrote:

See http://www.ibr.cs.tu-bs.de/cgi-bin/sbrowser.cgi


To expand a little, OIDs under the above should have corresponding ones with
the interface index under 1.3.6.1.2.1.4.20.1.2. AIUI it's permissable for an
interface index to change when the system is reinitialised, but IME that
doesn't happen unless the hardware is changed, and that won't happen in a
router. So, as a one-off, you can manually find the interface index for the
router's WAN port. Then (in your DNS update client) you can poll (walking
...1 and ...2) to find the address associated with that interface.

That said, it's undoubtedly easier and probably satisfactory just to walk
the address entries looking for a routable address.


Thanks for that. I'm currently trying to find out how the requests are
structured, but only half heartedly, as I'm sporting the latest
fashionable lurgii, the super-intense coldie-fluie one.. (

Slightly annoying as I've seen at least one presentation that described
the packets in lovely detail, discovered by accident when I was revising
for an (almost unrelated) exam, but it seems to have disappeared from my
history file..

--
Dave Johnson -
  #5  
Old January 10th 05, 05:16 PM posted to uk.comp.home-networking
Alex Fraser
external usenet poster
 
Posts: 553
Default SNMP and external IP

"Dave J" wrote in message
...
In within uk.comp.home-networking,
'Alex Fraser' wrote:

[snip]
Thanks for that. I'm currently trying to find out how the requests are
structured, but only half heartedly, as I'm sporting the latest
fashionable lurgii, the super-intense coldie-fluie one.. (


Unless you have some pressing need to construct/parse packets yourself, you
might save time by using the Net-SNMP library, http://www.net-snmp.org/.
Even if you don't want to use it, the command-line tools it comes with will
probably be useful.

Alex


 




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