API Guide

More path support
More path (Add-Path) reduces convergence times by advertising multiple paths to its peers for the same address prefix without
replacing existing paths with new ones. By default, a BGP speaker advertises only the best path to its peers for a given address
prefix.
If the best path becomes unavailable, the BGP speaker withdraws its path from its local router information base (RIB) and
recalculates a new best path. This situation requires both IGP and BGP convergence and is a lengthy process. BGP add-path
also helps switch over to the next new best path when the current best path is unavailable.
The Add-Path capability to advertise more paths is supported only on IBGP peers—it is not supported on EBGP peers or BGP
peer groups.
Ignore router ID calculations
Avoid unnecessary BGP best path transitions between external paths under certain conditions. The bestpath router-id
ignore command reduces network disruption that is caused by routing and forwarding plane changes and allows for faster
convergence.
Advertise cost
As the default process for redistributed routes, OS10 supports IGP cost as MED. Both autosummarization and synchronization
are disabled by default.
BGPv4 and BGPv6 support
● Deterministic MED, default
● A path with a missing MED is treated as worst path and assigned an 0xffffffff MED value.
● Delayed configuration at system boot—OS10 reads the entire configuration file BEFORE sending messages to start BGP
peer sessions.
4-Byte AS numbers
OS10 supports 4-byte AS number configurations by default. The 4-byte support is advertised as a new BGP capability - 4-
BYTE-AS, in the OPEN message. A BGP speaker that advertises 4-Byte-AS capability to a peer, and receives the same from
that peer must encode AS numbers as 4-octet entities in all messages.
If the AS number of the peer is different, the 4-byte speaker brings up the neighbor session using a reserved 2-byte ASN, 23456
called AS_TRANS. The AS_TRANS is used to interop between a 2-byte and 4-byte AS number.
Where the 2-byte format is 1 to 65535, the 4-byte format is 1 to 4294967295. You can also enter AS numbers using the dotted
decimal format. For example, you can enter 0.123.
Layer 3
579