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howto check duplex mode from any network devices in LAN ?

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'chris'
Super Advisor

howto check duplex mode from any network devices in LAN ?

hi

I have 2 questions:

1.) howto check duplex mode from any network devices in LAN ?
for Example, I have a router or firewall in LAN or WAN, but don't have an access.
maybe is it possible to find out if I have a SNMP READ ONLY enabled on these devices ?

2:)I have watchguard firewall and don't know its duplex mode: FD,HD,AUTO ?
If I set the switch to AUTO or HD, then I get errors.
Without errors, it works only in HD mode.
If one device works in HALF DUPLEX mode without errors, then how was setup the second one: FD,HD,AUTO ?

kind regards
chris








2 REPLIES
Terhorst
Trusted Contributor
Solution

Re: howto check duplex mode from any network devices in LAN ?

Hi Chris,

With SNMP and read-only it should be possible to get the duplex status. You must know what mibs are supported by the device. For instance if the etherlike-mib (RFC2665) is supported you could read it from the dot3StatsDuplexStatus

(1.3.6.1.2.1.10.7.2.1.19
-- iso(1). org(3). dod(6). internet(1). mgmt(2). mib-2(1). transmission(10). dot3(7). dot3StatsTable(2). dot3StatsEntry(1). dot3StatsDuplexStatus(19)
SYNTAX INTEGER {
unknown (1),
halfDuplex (2),
fullDuplex (3)
}

MAX-ACCESS read-only
DESCRIPTION
"The current mode of operation of the MAC
entity. 'unknown' indicates that the current
duplex mode could not be determined.
Management control of the duplex mode is
accomplished through the MAU MIB. When
an interface does not support autonegotiation,
or when autonegotiation is not enabled, the
duplex mode is controlled using
ifMauDefaultType. When autonegotiation is
supported and enabled, duplex mode is controlled
using ifMauAutoNegAdvertisedBits. In either
case, the currently operating duplex mode is
reflected both in this object and in ifMauType.

Note that this object provides redundant
information with ifMauType. Normally, redundant
objects are discouraged. However, in this
instance, it allows a management application to
determine the duplex status of an interface
without having to know every possible value of
ifMauType. This was felt to be sufficiently
valuable to justify the redundancy."
REFERENCE
"[IEEE 802.3 Std.], 30.3.1.1.32,
aDuplexStatus."
::= { dot3StatsEntry 19 }

If you have the correct community string, just try with snmpget, snmpgetnext or snmpwalk.

The firewall probably only support 10 Mbps halfduplex. In that case, it is preferable to set the switch in halfduplex mode.

Regards,
Alexander


Regards
Les Ligetfalvy
Esteemed Contributor

Re: howto check duplex mode from any network devices in LAN ?

I think you must have made a typo (HD instead of FD) because you contradict yourself.
If I set the switch to AUTO or HD, then I get errors.
Without errors, it works only in HD mode.


You don't mention what speed the firewall works at. I too suspect that it is 10/half. Old hub technology was 10/half and was much more prevalent than 10/full which was quickly overshadowed by 100 meg technology. In other words, there is a lot more 10/half out there than 10/full.

What is the circumstance that you do not know the snmp community for the firewall? If it managed by a different group? Of course you could try using the default "public" but any management group worth their salt would have changed it. They most likely would deny you all snmp access as well if the device is so capable.

If you are just cutting your teeth on snmp, I suggest you get yourself a decent snmp MI browser. I use MG-SOFT ( http://www.mg-soft.com/index.html ). Download and complile the MIBs for all your devices. You could delve into all the RFCs to get an understanding of how the MIBs work, or you could start by just reading through the uncompiled MIBs.

Kinda makes one wonder where the "simple" is in SNMP? :-/