The BGP hold time specifies the maximum time BGP will wait between successive messages (either keep alive or update) from its peer, before closing the connection. This configuration parameter can be set at three levels. The most specific value is used.
Global level — applies to all peers
Group level — applies to all peers in group
Neighbor level — only applies to specified peer
Although the keep alive time can be user specified, the configured keep alive timer is overridden by the value of hold time under the following circumstances:
If the hold time specified is less than the configured keep alive time, then the operational keep alive time is set to one third of the specified hold time; the configured keep alive time is unchanged.
If the hold time is set to zero, then the operational value of the keep alive time is set to zero; the configured keep alive time is unchanged. This means that the connection with the peer will be up permanently and no keep alive packets are sent to the peer.
If the hold time or keep alive values are changed, the changed timer values take effect when the new peering relationship is established. Changing the values cause the peerings to restart. The changed timer values are used when renegotiating the peer relationship.