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# global configuration

ASNUM=»64600″
IP=»10.255.255.10″
LAN=»10.255.255.0/24″
AS $ASNUM
router-id $IP
transparent-as yes

fib-update no
log updates

network $LAN

group RS {
announce all
max-prefix 5000 restart 15
set nexthop no-modify
# softreconfig in no

neighbor $LAN {
descr «RS peer»
passive
}
}

# filter out prefixes longer than 24 or shorter than 8 bits
deny from any prefix 0.0.0.0/0 prefixlen 8 >< 24

# do not accept a default route, multicast and experimental networks
deny from any prefix 0.0.0.0/0
deny from any prefix 10.0.0.0/8 prefixlen >= 8
deny from any prefix 127.0.0.0/8 prefixlen >= 8
deny from any prefix 169.254.0.0/16 prefixlen >= 16
deny from any prefix 172.16.0.0/12 prefixlen >= 12
deny from any prefix 192.0.2.0/24 prefixlen >= 24
deny from any prefix 192.168.0.0/16 prefixlen >= 16
deny from any prefix 224.0.0.0/4 prefixlen >= 4
deny from any prefix 240.0.0.0/4 prefixlen >= 4

# we set’s these communities to identify from where
# it learned a route:
match from any set community $ASNUM:neighbor-as

# 1. Prepend RS $ASNUM to *all* RS-Peers
match from group RS community $ASNUM:64600 set prepend-self 1

# 2. Prepend RS $ASNUM to *selected* RS-Peer N-times
# (N can be 1 to 3)
match to group RS community 64601:neighbor-as set prepend-self 1
match to group RS community 64602:neighbor-as set prepend-self 2
match to group RS community 64603:neighbor-as set prepend-self 3

# 3. Do *not* announce to RS-Peers with AS AAAA
deny to group RS community $ASNUM:neighbor-as

# 4. Do *not* announce to *ANY* RS-Peers
deny to group RS community $ASNUM:65535

# 5. Prepend own announcement by one
match to group RS prefix $LAN set prepend-self 1

(c) http://www.mail-archive.com/misc@openbsd.org/msg68217.html