Ignore Cisco reserved VLANs when collecting BRIDGE-MIB data

[Morten Brekkevold]

Many Cisco IOS versions reserve the VLANs 1002-1005 for internal purposes (FDDI and Token Ring related, see http://etherealmind.com/cisco-ios-vlan-1002-reserved-1005-purpose-function/).

Since these aren't ethernet VLANs, they have no corresponding BRIDGE-MIB instance to query. These VLANs are reported as operational in the vtpVlanTable, but any attempt to query the BRIDGE-MIB for these VLANs will time out. This causes the ipdevpoll topo job to run amazingly slow, and will also delay switch port detection on Cisco switches in the inventory job.

The CISCO-VTP-MIB::vtpVlanTable also features the vtpVlanType column, which can be used to filter out anything that isn't an ethernet VLAN. NAV should ignored non-ethernet VLANs, thus saving a lot of time.

[Morten Brekkevold (mbrekkevold)]

fix here: https://nav.uninett.no/hg/stable/rev/a1efff9d5210