Configuring Passive Peering; Maintaining Existing As Numbers During An As Migration - Dell S4048–ON Configuration Manual

Configuring Passive Peering

When you enable a peer-group, the software sends an OPEN message to initiate a TCP connection.
If you enable passive peering for the peer group, the software does not send an OPEN message, but it responds to an OPEN
message.
When a BGP neighbor connection with authentication configured is rejected by a passive peer-group, Dell Networking OS does not
allow another passive peer-group on the same subnet to connect with the BGP neighbor. To work around this, change the BGP
configuration or change the order of the peer group configuration.
You can constrain the number of passive sessions accepted by the neighbor. The limit keyword allows you to set the total number
of sessions the neighbor will accept, between 2 and 265. The default is 256 sessions.
1. Configure a peer group that does not initiate TCP connections with other peers.
CONFIG-ROUTER-BGP mode
neighbor peer-group-name peer-group passive limit
Enter the limit keyword to restrict the number of sessions accepted.
2. Assign a subnet to the peer group.
CONFIG-ROUTER-BGP mode
neighbor peer-group-name subnet subnet-number mask
The peer group responds to OPEN messages sent on this subnet.
3. Enable the peer group.
CONFIG-ROUTER-BGP mode
neighbor peer-group-name no shutdown
4. Create and specify a remote peer for BGP neighbor.
CONFIG-ROUTER-BGP mode
neighbor peer-group-name remote-as as-number
Only after the peer group responds to an OPEN message sent on the subnet does its BGP state change to ESTABLISHED. After the
peer group is ESTABLISHED, the peer group is the same as any other peer group.
For more information about peer groups, refer to

Maintaining Existing AS Numbers During an AS Migration

The local-as feature smooths out the BGP network migration operation and allows you to maintain existing ASNs during a BGP
network migration.
When you complete your migration, be sure to reconfigure your routers with the new information and disable this feature.
• Allow external routes from this neighbor.
CONFIG-ROUTERBGP mode
neighbor {IP address | peer-group-name local-as as number [no prepend]
– Peer Group Name: 16 characters.
– AS-number: 0 to 65535 (2-Byte) or 1 to 4294967295 (4-Byte) or 0.1 to 65535.65535 (Dotted format).
– No Prepend: specifies that local AS values are not prepended to announcements from the neighbor.
Format: IP Address: A.B.C.D.
You must Configure Peer Groups
194
Border Gateway Protocol IPv4 (BGPv4)
Configure Peer
before assigning it to an AS. This feature is not supported on passive peer groups.
Groups.