IBM 9077 Spamming, Bridging Components, Bridging Daemon Bridged, Configuration File bridged.conf

A frame may be too large for the maximum transmission unit (MTU) of the sending GRF interface. One example is when forwarding a 4500-byte frame from FDDI to an Ethernet interface with an MTU of 1500 bytes. The GRF bridge will attempt to break such a frame into fragments that will fit the sending interface. This is possible if the frame contains an IP datagram; then the GRF may use the fragmentation rules of IP to split the frame. Otherwise, the GRF must drop the frame.

4.6.8 Spamming

Spamming is when a bridging interface forwards a frame to all active interfaces in the bridge group. On the GRF, spamming is done when a broadcast address is received or when a frame arrives whose destination address is not in the bridge filtering table.

4.6.9 Bridging Components

The following subsections discuss the various bridging components.

4.6.9.1 Bridging Daemon – Bridged

The bridging daemon, bridged, is used to configure and manipulate bridging interfaces on the GRF. It operates the spanning tree algorithm specified in IEEE 802.1d and ensures interoperability with other 802.1d bridges.

Bridged reads the /etc/bridged.conf configuration file to build an initial bridging topology.

Bridged is started by the system script /etc/grstart. This script monitors the bridged daemon and restarts it if it stops.

4.6.9.2 Configuration File – bridged.conf

The bridging configuration file is /etc/bridged.conf. A utility, bredit, is used to access the file and create bridge groups and bridging settings.

Parameters in bridged.conf can be set to do the following:

•Name bridge groups

•Assign logical interfaces to a group

•Assign priority, starting state, root path cost, and forwarding addresses to individual logical interfaces

•Assign hello time and forwarding delay values, priority, maximum age, and discard addresses to individual groups

Configuration of IP-Forwarding Media Cards 145