Appendix B. Custom Network Properties

B.1. Explanation of bridge_opts Parameters

Table B.1. bridge_opts parameters

Parameter Description
forward_delay Sets the time, in deciseconds, a bridge will spend in the listening and learning states. If no switching loop is discovered in this time, the bridge will enter forwarding state. This allows time to inspect the traffic and layout of the network before normal network operation.
gc_timer Sets the garbage collection time, in deciseconds, after which the forwarding database is checked and cleared of timed-out entries.
group_addr Set to zero when sending a general query. Set to the IP multicast address when sending a group-specific query, or group-and-source-specific query.
group_fwd_mask Enables bridge to forward link local group addresses. Changing this value from the default will allow non-standard bridging behavior.
hash_elasticity The maximum chain length permitted in the hash table. Does not take effect until the next new multicast group is added. If this cannot be satisfied after rehashing, a hash collision occurs and snooping is disabled.
hash_max The maximum amount of buckets in the hash table. This takes effect immediately and cannot be set to a value less than the current number of multicast group entries. Value must be a power of two.
hello_time Sets the time interval, in deciseconds, between sending 'hello' messages, announcing bridge position in the network topology. Applies only if this bridge is the Spanning Tree root bridge.
hello_timer Time, in deciseconds, since last 'hello' message was sent.
max_age Sets the maximum time, in deciseconds, to receive a 'hello' message from another root bridge before that bridge is considered dead and takeover begins.
multicast_last_member_count Sets the number of 'last member' queries sent to the multicast group after receiving a 'leave group' message from a host.
multicast_last_member_interval Sets the time, in deciseconds, between 'last member' queries.
multicast_membership_interval Sets the time, in deciseconds, that a bridge will wait to hear from a member of a multicast group before it stops sending multicast traffic to the host.
multicast_querier Sets whether the bridge actively runs a multicast querier or not. When a bridge receives a 'multicast host membership' query from another network host, that host is tracked based on the time that the query was received plus the multicast query interval time. If the bridge later attempts to forward traffic for that multicast membership, or is communicating with a querying multicast router, this timer confirms the validity of the querier. If valid, the multicast traffic is delivered via the bridge's existing multicast membership table; if no longer valid, the traffic is sent via all bridge ports. Broadcast domains with, or expecting, multicast memberships should run at least one multicast querier for improved performance.
multicast_querier_interval Sets the maximum time, in deciseconds, between last 'multicast host membership' query received from a host to ensure it is still valid.
multicast_query_use_ifaddr Boolean. Defaults to '0', in which case the querier uses 0.0.0.0 as source address for IPv4 messages. Changing this sets the bridge IP as the source address.
multicast_query_interval Sets the time, in deciseconds, between query messages sent by the bridge to ensure validity of multicast memberships. At this time, or if the bridge is asked to send a multicast query for that membership, the bridge checks its own multicast querier state based on the time that a check was requested plus multicast_query_interval. If a multicast query for this membership has been sent within the last multicast_query_interval, it is not sent again.
multicast_query_response_interval Length of time, in deciseconds, a host is allowed to respond to a query once it has been sent. Must be less than or equal to the value of the multicast_query_interval.
multicast_router Allows you to enable or disable ports as having multicast routers attached. A port with one or more multicast routers will receive all multicast traffic. A value of 0 disables completely, a value of 1 enables the system to automatically detect the presence of routers based on queries, and a value of 2 enables ports to always receive all multicast traffic.
multicast_snooping Toggles whether snooping is enabled or disabled. Snooping allows the bridge to listen to the network traffic between routers and hosts to maintain a map to filter multicast traffic to the appropriate links. This option allows the user to re-enable snooping if it was automatically disabled due to hash collisions, however snooping will not be re-enabled if the hash collision has not been resolved.
multicast_startup_query_count Sets the number of queries sent out at startup to determine membership information.
multicast_startup_query_interval Sets the time, in deciseconds, between queries sent out at startup to determine membership information.