Confused about route-map

Question

I'm playing around with BGP on Quagga.

I have three routers, R1, R2 and R3, connected in sequence and have R2 and R3 send a few routes to R1.

R1 -- R2 -- R3

Configuration of R1:

router bgp 10
router-id 1.1.1.1
network 10.10.10.0 255.255.255.0
network 12.12.12.0 255.255.255.0
network 192.168.2.0 255.255.255.0
neighbor 192.168.2.23 remote-as 10
neighbor 10.10.10.2 remote-as 20
neighbor 10.10.10.2 route-map D1 in
exit

ip as-path access-list 20 permit 30$

route-map D1 deny 90
match as-path 20
exit

Configuration of R2:

router bgp 20
router-id 2.2.2.2
network 10.10.10.0 255.255.255.0
network 20.20.20.0 255.255.255.0
neighbor 10.10.10.1 remote-as 10
neighbor 20.20.20.3 remote-as 30
exit

Configuration of R3:

router bgp 30
router-id 3.0.3.33
network 20.20.20.0 255.255.255.0
network 30.30.30.0 255.255.255.0
neighbor 20.20.20.2 remote-as 20
exit

This setup ended up that route-map on R1 has removed all routes it has received.

I thought I would only remove routes from AS 30?

I have no experience on Cisco routers or else, so I cannot tell if it is an implementation bug or intended.

Answer 1

Like access lists, route-maps have an implicit "deny all" at the end. Stanza 90 denies packets it matches, and then everything else is denied by the implicit deny. You need a "permit all" statement at the end like this:

ip as-path access-list 20 permit 30$

route-map D1 deny 90
match as-path 20

route-map D1 permit 100

exit