Capability Negotiation - Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual

JUNOSe 11.1.x BGP and MPLS Configuration Guide
Suppose a BGP speaker has three routes to prefix 10.10.0.0/16:
BGP compares these routes to each other to determine the best path to the prefix.
If you have issued the bgp bestpath med confed command, BGP takes into account
the MED when comparing Route 1 with Route 2. However, BGP does not take into
account the MED when comparing Route 3 with either Route 1 or Route 2, because
Route 3 originates outside the confederation.

Capability Negotiation

The router accepts connections from peers that perform capability negotiation.
Capabilities are negotiated by means of the open messages that are exchanged when
the session is established. The router supports the following capabilities:
126
Selecting the Best Path
host1(config-router)#bgp bestpath med confed
Changes apply automatically whenever BGP subsequently runs the best-path
decision process for a destination prefix; that is, whenever a best route is picked
for a given prefix.
To force BGP to run the decision process on routes already received, you must
use the clear ip bgp command to perform an inbound soft clear or hard clear
of the current BGP session.
Use the no version to restore the default, where the MED is not taken into
account.
Route 1 is originated by sub-AS 1 inside the confederation.
Route 2 is originated by sub-AS 2 inside the confederation.
Route 3 is originated by AS 3 outside the confederation.
See bgp bestpath med confed.
Cisco-proprietary route refresh Capability code 128
Cooperative route filtering Capability code 3
Deprecated dynamic capability negotiation Capability code 66
Dynamic capability negotiation Capability code 67
Four-octet AS numbers Capability code 65
Graceful restart Capability code 64
Multiprotocol extensions Capability code 1
address family IPv4 unicast AFI 1 SAFI 1
address family IPv4 multicast AFI 1 SAFI 2
address family IPv4 unicast and multicast AFI 1 SAFI 3
address family VPN-IPv4 unicast AFI 1 SAFI 128
Route refresh Capability code 2