Filter Rules - MikroTik RouterOS v2.9 Reference Manual

with these prefixes. A rule with no arguments applies to all prefixes and implies accept action.
The routing filters may be applied to incoming and outgoing routing update messages for a specific
BGP peer and to outgoing BGP update messages for a particular BGP instance. Note, that in case
both BGP instance and BGP peer outgoing filters are applied, BGP instance filters take precedence.
Additional Documents
• http://www.ietf.org/rfc/rfc1771.txt
• http://www.cisco.com/univercd/cc/td/doc/cisintwk/ics/icsbgp4.htm
• http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2003.htm

Filter Rules

Property Description
action ( accept | discard | jump | none | reject | return ; default: none ) - action to perform on route
or route attributes for the NLRI prefixes that match the rule
• accept - accept the routing information for the matching NLRI prefix
• discard - completely exclude matching prefix from the BGP processing. The route will be
deleted from the incoming BGP routing update message, thus reducing memory usage on the
router. For outgoing BGP update messages the discard action is equal to reject
• jump - pass control to another filter list that should be specified as jump-target parameter
• none - do not perform any action and pass execution to the next rule in chain. The none action
is not displayed by print command
• reject - reject the routing information for matching prefix. The prefix from incoming BGP
routing update message is be shown with R (rejected) flag in the /ip route print command
output. The prefix is suppressed from outgoing routing update message
• return - return to the previous chain from which a jump to the current chain took place
as-path ( text ) - unanchored pattern to be searched inside AS_PATH attribute of the route.
Optional ^ sign preceiding parameter value restricts match to the beginning of AS_PATH attribute,
while $ sign, which follows as-path value, restricts the match to the end of AS_PATH
as-path-length ( integer | integer ) - length of the AS_PATH attribute, representing the number of
ASs that have been traversed. Note that multiple AS_SETs are combined together and counted as 1
AS
atomic-aggregate ( absent | present ) - match for the ATOMIC_AGGREGATE BGP attribute
chain ( text ) - chain name to place this rule in. If a chain with the specified name does not exist it
will be automatically created
distance ( integer | integer ; default: no ) - protocol-independent administrative distance used to
compare routes obtained from different sources
jump-target ( name ) - name of the target chain to jump to, if the action=jump is used
local-pref ( integer | integer ) - match for the LOCAL_PREF BGP attribute
match-chain ( name ) - the name of the chain which is used to evaluate the route. If the chain
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