An alternative local AS number that can be used to establish a session with peers in this peer group. This is used when merging two ASs into a single AS. For individual peers, this can be configured using bgpPeerConfAltLocalAs. A value of zero means 'not configured'. If an alternative local AS number is configured then the peering session can be established using the alternative local AS instead of the primary local AS number specified by bgpRmEntLocalAs. Setting an alternative local AS number allows the primary local AS number to be changed without reconfiguring the peers in this peer group at the same time. Later the peers can be reconfigured to establish the session using the new remote AS number and the alternative local AS number can be reset to zero. An alternative local AS number should only be used as an intermediate step on one side of a BGP session. Do not configure an alternative local AS number on both sides of a BGP session - configure the correct remote AS numbers instead. Use of alternative local AS numbers is not supported if the router is a member of a confederation. This field can be changed at any time. However, if a peer is configured to use the peer group field and the field is changed while the peer is active, depending on the setting of the bgpPeergrResetPeerOnCfgChange field, the peer session may either be immediately reset, or the configuration change is not applied until the peer session is restarted.