Connectivity Guide

The Local-AS does not prepend the updates with the AS number received from the EBGP peer if you use the no prepend
command. If you do not select no prepend, the default, the Local-AS adds to the first AS segment in the AS-PATH. If you use
an inbound route-map to prepend the AS-PATH to the update from the peer, the Local-AS adds first.
If Router B has an inbound route-map applied on Router C to prepend 65001 65002 to the AS-PATH, these events take place
on Router B:
● Receive and validate the update.
● Prepend local-as 200 to AS-PATH.
● Prepend 65001 65002 to AS-PATH.
Local-AS prepends before the route map to give the appearance that the update passed through a router in AS 200 before it
reaches Router B.
Configure Border Gateway Protocol
BGP is disabled by default. To enable the BGP process and start to exchange information, assign an AS number and use
commands in ROUTER-BGP mode to configure a BGP neighbor.
BGP neighbor
adjacency
changes
All BGP neighbor changes are logged
Fast external
fallover
Enabled
Graceful restart Disabled
Local preference 100
4-byte AS Enabled
MED 0
Route flap
dampening
parameters
● half-life = 15 minutes
● max-suppress-time = 60 minutes
● reuse = 750
● suppress = 2000
Timers
● keepalive = 60 seconds
● holdtime = 180 seconds
Add-path Disabled
Enable BGP
Before enabling BGP, assign a BGP router ID to the switch using the following command:
● In the ROUTER BGP mode, enter the router-id ip-address command. Where in, ip-address is the IP address
corresponding to a configured L3 interface (physical, loopback, or LAG).
BGP is disabled by default. The system supports one AS number — you must assign an AS number to your device. To
establish BGP sessions and route traffic, configure at least one BGP neighbor or peer. In BGP, routers with an established TCP
connection are called neighbors or peers. After a connection establishes, the neighbors exchange full BGP routing tables with
incremental updates afterward. Neighbors also exchange the KEEPALIVE messages to maintain the connection.
You can classify BGP neighbor routers or peers as internal or external. Connect EBGP peers directly, unless you enable EBGP
multihop — IBGP peers do not need direct connection. The IP address of an EBGP neighbor is usually the IP address of the
interface directly connected to the router. The BGP process first determines if all internal BGP peers are reachable, then it
determines which peers outside the AS are reachable.
Layer 3
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