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Remote-triggered BGP blackhole posted 02/01/2007
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Hi,

I'm having a hard time with my remote triggered BGP blackhole config
Router4 should change the next-hop to 192.0.2.1 instead of 4.4.4.4 (it's
loopback), But I do not see that behaviour.



I have 2 routers with the following config:

ROUTER4:
========================
router bgp 345 bgp router-id 4.4.4.4 no bgp default ipv4-unicast no bgp
default route-target filter bgp log-neighbor-changes neighbor 5.5.5.5
remote-as 345 neighbor 5.5.5.5 update-source Loopback0 ! address-family ipv4
redistribute static metric 1 route-map black   <---- route-map for BGP
blackhole neighbor 5.5.5.5 activate neighbor 5.5.5.5 next-hop-self neighbor
5.5.5.5 send-community neighbor 5.5.5.5 soft-reconfiguration inbound neighbor
5.5.5.5 send-label no auto-summary no synchronization network 4.4.4.4 mask
255.255.255.255 exit-address-family !
route-map black permit 10 match tag 99 set ip next-hop 192.0.2.1 set origin
igp set community no-export!ip route 44.44.44.44 255.255.255.255 Null0 tag
99ip route 192.0.2.0 255.255.255.0 Null0
SHOW OUTPUT:
R4#show ip bgp | inc 44.44*> 44.44.44.44/32   192.0.2.1                1
32768 iR4#show ip route 44.44.44.44Routing entry for 44.44.44.44/32  Known via
"static", distance 1, metric 0 (connected)  Tag 99  Redistributing via bgp 345
Advertised by bgp 345 metric 1 route-map black  Routing Descriptor Blocks:  *
directly connected, via Null0      Route metric is 0, traffic share count is 1
Route tag 99

Looks fine....

BUT!!


ROUTER5:
=============
ip route 192.0.2.0 255.255.255.0 Null0

router bgp 345 bgp router-id 5.5.5.5 no bgp default ipv4-unicast no bgp
default route-target filter bgp log-neighbor-changes neighbor IBGP peer-group
neighbor IBGP remote-as 345 neighbor IBGP update-source Loopback0 neighbor
4.4.4.4 remote-as 345 neighbor 4.4.4.4 peer-group IBGP neighbor 4.4.4.4
update-source Loopback0 ! address-family ipv4 neighbor IBGP activate neighbor
IBGP route-reflector-client neighbor IBGP next-hop-self neighbor IBGP
send-community neighbor IBGP route-map path out neighbor IBGP send-label
neighbor 4.4.4.4 peer-group IBGP no auto-summary no synchronization network
5.5.5.5 mask 255.255.255.255 exit-address-family
============
R5#show ip route 192.0.2.1Routing entry for 192.0.2.0/24  Known via "static",
distance 1, metric 0 (connected)  Routing Descriptor Blocks:  * directly
connected, via Null0      Route metric is 0, traffic share count is 1
R5#show ip rout 44.44.44.44Routing entry for 44.44.44.44/32  Known via "bgp
345", distance 200, metric 1, type internal  Last update from 4.4.4.4 00:09:06
ago  Routing Descriptor Blocks:  * 4.4.4.4, from 4.4.4.4, 00:09:06 ago
Route metric is 1, traffic share count is 1      AS Hops 0R5#show ip bgp | inc
44.44*>i44.44.44.44/32   4.4.4.4                  1    100      0 iR5#show ip
bgp neighbors 4.4.4.4 received-routesBGP table version is 17, local router ID
is 5.5.5.5Status codes: s suppressed, d damped, h history, * valid, > best, i
- internal,              S StaleOrigin codes: i - IGP, e - EGP, ? -
incomplete
   Network          Next Hop            Metric LocPrf Weight Path*>i4.4.4.4/32
4.4.4.4                  0    100      0 i*>i44.44.44.44/32   4.4.4.4
1    100      0 i    <<=== SO ROUTER4 (lo0: 4.4.4.4) is not changing the
next-hop to 192.0.2.1???
ROUTER4
========
R4#show ip bgp neighbors 5.5.5.5 advertised-routesBGP table version is 233,
local router ID is 4.4.4.4Status codes: s suppressed, d damped, h history, *
valid, > best, i - internal,              S StaleOrigin codes: i - IGP, e -
EGP, ? - incomplete
   Network          Next Hop            Metric LocPrf Weight Path*> 4.4.4.4/32
0.0.0.0                  0         32768 i*> 44.44.44.44/32   192.0.2.1
1         32768 i  <====== Huh... it's changing the next-hop to 192.0.2.1.



I do not get it..

When redistributing the static route into BGP (on R4) it should match the tag
99, and change the next-hop to "192.0.2.1", then R5 should drop the packet
locally to Null0, since it has a static route for 192.0.2.0/24 pointing to
Null0...

What's wrong with my config!

Thanks guys and girls



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