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I recently switched to a Netgear WNDR3700 (v2) running DD-WRT v24-sp2 (02/19/11) std. It's basically working fine and I'm generally happy with it, but any tools that query the router via SNMP show all the interfaces as being 10 mbit. In fact, the LAN interfaces are gigabit, and the wireless interface is 54 mbit (or thereabouts).

This isn't a huge deal, except that when I try to set up alarms based on current interface use being over a certain percentage of maximum, I run into problems.

I'm unable to find anywhere in the DD-WRT interface to specify interface limits. Where does the router's SNMP service get this information? I'm able to access DD-WRT via SSH command line, so I'm wondering about the possibility of using Linux commands or configuration files to set the limits correctly. Is that even possible?

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Have you verified that the duplexing on the port is indeed set to something other than 10mbit? The port itself may be gigabit, but if the duplexing is set otherwise, it will read as it is set. – MaQleod May 21 '11 at 3:02
@MaQleod: Sounds promising. Now... how would I go about doing that? – boot13 May 21 '11 at 6:01
dd-wrt.com/phpBB2/viewtopic.php?t=556 might help you out. It is also important to note that the duplexing to whatever the WAN on your DDWRT router is connected to needs to match. It is very likely that the router is set to auto negotiate and the other device is 10 full or half, so it is negotiating to that. If you try to force 100 or 1000 on the router and the other device actually is set to 10, then you'll get a lot of other problems with bandwidth, latency and loss between the devices. – MaQleod May 21 '11 at 21:10
@MaQleod: No Setup > VLANs tab in my DD-WRT interface. The page you linked to is from 2006, so maybe DD-WRT has changed a bit. I'm not convinced that the bandwidths are actually set incorrectly; I'm thinking it's more of an SNMP problem. I'm getting better than 10 Mbits on the WAN interface in speed tests. The LAN connection goes to a switch that is set to autoconfigure and shows the connection as gigabit, and yet SNMP information from the router says it's 10 mbit. – boot13 May 21 '11 at 23:31
Sorry, I don't use DDWRT, but I deal with duplexing and snmp issues on a daily basis, so unfortunately I can't help out much with DDWRT specifics. – MaQleod May 22 '11 at 0:29
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It's most likely that net-snmp isn't detecting the interface speed correctly. You can manually configure the speed in snmpd.conf:

    interface NAME TYPE SPEED
          can  be  used to provide appropriate type and speed settings for
          interfaces where the agent fails to determine  this  information
          correctly.  TYPE is a type value as given in the IANAifType-MIB,
          and can be specified numerically or by name (assuming  this  MIB
          is loaded)
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