Specifications

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§ route flap dampening - The Juniper BGP4 implementation contains the
route dampening feature and its configuration includes the ability to enable
and disable it as well as to configure the various penalties, half-lives and
suppression thresholds. Disabling the default route flap damping behavior
can be based on policy, on a per prefix and/or per peer basis, as per the
example below :
[edit policy-options]
damping dont-damp {
disable;
}
policy-statement test {
from {
route-filter 198.41.0.0/22 exact;
[…]
route-filter 198.32.65.0/24 exact;
}
then {
damping dont-damp;
accept;
}
}
§ community, MED, local-pref attributes - The Juniper BGP implementation
includes the BGP community, MULTI-EXIT-DISCRIMINATOR and LOCAL-
PREF attributes. In addition, these attributes are fully incorporated into the
policy engine, allowing routes exchanged with BGP to be accepted or
rejected based on these attributes and also allowing the attributes
associated with a prefix to be added, deleted or changed
§ Extended communities - Provides an extended range, ensuring that
communities can be assigned for many uses without overlap and provides
structure for the community space (moving from 4 to 8 octets) by the
addition of a Type field (2 octets) which structures the space :
o 0x0000 – 0x7fff : Assigned by IANA
o 0x8000 – 0xffff : Vendor specific
The Value field has 6 octets which contain either:
o Administrator field: Contains either AS number or IPv4 Address
prefix
o Assigned Number: Local provider value
Extended Communities allow you to filter out all communities of a particular
type or only to set certain values for a particular type of community
Supported Communities are :
o Route target community: Identifies routers which should receive a
set of routes
o Route origin community: Identifies which routers inject which routes
§ match and reset nexthop, MED, local-pref attributes - The NEXT-HOP,
MULTI-EXIT-DISCRIMINATOR and LOCAL-PREF attributes are fully
incorporated into the policy engine, so their values can be matched against
to policy for modification or route selection.
§ match, append or reset community & as-path attributes - The policy
engine completely supports matching against the BGP community and AS-
Path attributes to decide whether to accept a prefix. If a prefix is accepted,
the values in the community attribute can be deleted, appended to or
changed and/or the AS-Path attribute can be prepended with particular
ASNs. The configuration related to BGP communities includes the ability to
Type AS Number Assigned Number
Type Assigned #IPv4 Address
2 octets 2 octets4 octets
2 octets 2 octets 4 octets